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Cover picture“The Moon is a mystery”: this was the answer given to me by the presidentof the International Flat Earth Society during our radio debate (www.universalworkshop.com/Litfoam/FlatEarth.htm). I had no real hope that hewould listen to, let alone be persuaded by, the other arguments I had prepared,but the Full Moon is surely a simple clincher. We see its circular face staringdown at us; if the bright part of it is the half on which the Sun is shining—andby watching it through the other phases we are compelled to see that it is—thenthis must mean that the Sun is down in the opposite direction, under the ground-level we stand on. —No good: “The Moon is a mystery.”

Indeed it is; it has been taken for a f lying saucer, shot at with rif les. I remem-ber a long ride on the back of a pickup truck through a desert before dawn andthe driver stopping and asking: “What’s that over there?” He thought it was thelighted porch of a lonely trading post where we might get something to eat; itwas the horns of the Moon rising through bars of cloud.

You could say there is a paradox for each phase of the Moon. The famousone is the Moon Illusion: when the Moon is down low to the horizon it seemsstrikingly larger in our eyes (though it actually subtends a smaller angle, becauseof refraction and because more distant than when it is in the middle of the sky).And this, which has had books written about it and has scarcely been explained,is best seen when the Moon is Full. The New Moon is a mystery in a differentway: we infer it happens but can never see it—except at a solar eclipse, when theMoon suddenly manifests itself out of empty sky, and only as a silhouette. Theparadox I associate with the Last Quarter Moon (though it applies better to anyMoon that is clearly just past Full) isn’t really paradoxical and yet it carries a fris-son of surprise; it is one of those observations that make astronomical spacejump into three dimensions. You see the Sun go down over to your right in thewest, and some time later you notice the Moon above the horizon to your left.And its bright face. pointing slantingly downward, is evidently receiving a streamof sunlight that is coming up on the other side of Earth from that on which theSun went down. The Sun has slid around in some vast cavity behind you, andat this moment you feel the free-f loatingness of the world you stand on. It israther as if you thought you were in a house; then through a window notice waterf lowing toward you, and through an opposite window notice water f lowing away,and realize you are on a ship.

From a small town called Vernazza we watched the Sun go down—it becamea point exactly in that notch between sections of the mountain line farther westalong the Ligurian coast of Italy. An hour or so later, long enough for the skyto go black, we noticed the brilliant Moon above the dark rooftops. It lay in awash of its own dazzle, but within this it was a solid white D, because this wasthe moment of First Quarter, on the evening of May 28 last year.

Why does its D-shaped face gaze in a direction almost parallel to the hori-zon, instead of downward toward the Sun from which it is receiving its light?You could call this the First-Quarter Moon paradox, since this is when it is mostplainly displayed. The illuminated face does point straight toward the Sun, butwhat is “straight”? We are accustomed to thinking of the horizon as the straightline. Both the horizon and the ecliptic (the line along which the Sun travels andthe Moon approximately travels) are straight in the sense that they are “great cir-cles” around the sky. If we painted this picture on the inside of a coconut shell,the horizon would be a f lat line encircling the shell, and the ecliptic would beanother such f lat line, along which the Moon would face straight toward theSun. But when we draw on f lat canvas, we have to choose only one great circleto be f lat.

Or:

The Moon was in Leo (actually it was under his feet, dipping through the lit-tle constellation Sextans). Just up-right from the Moon was Regulus and just up-left from it Mars—it had passed Regulus during the day and would pass Marsduring the night. And that bright dot in the notch where the Sun set, like amemory of the Sun’s last glint, is Venus, though it couldn’t really be seen. It wasfollowing the Sun down by about an hour (to venture accurately in front of it,just four days later, at that rare event called a transit).

At this First Quarter moment it’s ninety degrees, a quarter of the circle, fromMoon to Sun. I thought that in the picture I had got this distance compressed,or the Moon’s height exaggerated—it’s a habit of our perception to exaggeratethe vertical at the expense of the horizontal—but it turns out to be about right.There may be some time-compression between twilight and black night sky. InItaly I found myself making Italy-shaped pictures, slanting from upper left tolower right, so as to get things in that were far apart. As it happens (because thelatitude of the place is near 45° and so is the slant of the ground as I’ve drawnit, if you hold the picture in “landscape mode,” the long edge is parallel to athird great circle: the equator. So the North Pole Star is straight upward, andthe scene is a magnified view of the edge of an Earth globe that you are hold-ing upright in your hands. Tilted views like this, as if from off the planet inspace, can make us feel that it really is a f loating globe, on which we cling likedust.

The town, like many on Italy’s steep coasts, consists of streetless piles of hous-es on either side of a former stream, now the only street, descending to the piaz-za (where boats are drawn up, one happening to be the dragon-headed racing

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galleon of Genoa). Our room (the lighted window) was approached not upstairs but up paths climbing inside the mass. The right-hand mass ends in thechurch, dedicated to Santa Margherita of Antioch and standing on a terrace withunder it what looks like a walled-up cave.

In a small street near the middle of Florence there is another church of SantaMargherita, where Dante is said to have seen Beatrice for the first time (she waseight and he nine) and where Beatrice is buried. He saw her only once more,nine years later. He married another (Gemma Donati, in 1285) and so did she(Simone de’ Bardi, in 1287), and she died in 1290 at age 24.

The great poem which Dante called just Comedy (because it ends—to say theleast—happily and because comedy did not have its modern meaning of “farce”)starts with him Nel mezzo del cammin’ di nostra vita, “At the midpoint of the high-way of our life,” that is, at the age of 35, on the day before Good Friday (March24, I think) in the year 1300, lost in a dark forest and confronted by terriblebeasts. From heaven Beatrice (whose “eyes outshone the light of any star”) seeshim and sends to rescue him the poet Virgil, his predecessor (by thirteen cen-turies) as composer of an Italian epic. Virgil first guides Dante down into hell,the Inferno, whose description constitutes the first of the three books of theDivine Comedy (as it later became called).

We don’t know where the dark forest of Dante’s despair was, in which he andhis guide found an arched entrance into the Inferno. They descended throughits nine circles, meeting and conversing with examples of every kind of sinner,and at the bottom the very worst, the traitors to their lords and benefactors:Judas Iscariot who took a bribe, Brutus and Cassius who stabbed the dictatorJulius Caesar, and Lucifer who rebelled against God. I would put quite others atthe bottom of my Inferno. Lucifer, “bearer of light,” was a title for the morningstar, Venus, but strangely became applied to the fallen angel Satan. Virgil andDante pass “the point to which all weight on every side pulls down” (the centerof the Earth) and then by using the gigantic shaggy body of Lucifer as a ladderthey climb out;

salimmo sù, el primo e io secondo,tanto ch’i’ vidi de le cose belleche porta ’l ciel, per un pertugio tondo.E quindi uscimmo a riveder le stelle.

We struggled up, first he and second I,Till I could see, as if through prison bars,Some of the lovely things that grace the sky.Thence came we out, to rebehold the stars.

(A mischievous translation, I’m afraid. Dante says “through a round aperture,”not “through prison bars.” I’m thinking not only of the rhyme but of prisonersI’ve known of, who longed to see the stars, or drew comfort from or wereabsolved by glimpsing them or learning about them, or were overjoyed to seethem on coming out.)

That’s how the Inferno ends. The second book, the Purgatorio, begins withwhat Dante immediately sees: Lo bel pianeto che d’amar conforta, “the fair planetthat empowers love”—Venus. So I imagined his point of emergence from theunderworld to be the seaside cave under this other church of Santa Margherita,with Venus on the skyline.

Unfortunately that can’t be, because he says that the planet was “making thewhole east smile” and was in Pisces, “veiling the Fishes that were in her train.”And, turning to the right, he looked “to the other pole, and saw four stars, neverbefore seen except by the primeval people,” non viste mai fuor che alla primagente—the Southern Cross. “The sky seemed to rejoice in their sparkling; ohwidowed region of the north, denied that sight!” Dante has penetrated throughthe Earth and emerged on the other side. The Inferno (a pit made by the fallof Lucifer) is under Jerusalem; at its antipodes, in an ocean that fills the south-ern hemisphere, is an island on which rises the Mount of Purgatory. In 1300 fewif any Europeans had explored south of the equator and thus seen the othercelestial pole, though plenty had been as far as Egypt and seen the SouthernCross. And Dante, without having been able to see those lands and constella-tions that the Earth hides, understood that it is a globe and that the Sun andstars roll around it; the time, he says, was sunset at Jerusalem and sunrise atMount Purgatory.

Virgil guides him up its seven levels, on which the redeemable sinners under-go their purification; on the highest terrace are those whose sins were caused bytoo much love. Toward the summit Virgil, being a pagan who can go no further,is replaced as guide by Beatrice, and she leads Dante through the EarthlyParadise, a Garden of Eden for those who have become innocent enough toqualify for Paradise itself. He drinks from the river and, like a tree with itsspring foliage, has become “pure and made fit to shoot up to the stars”—

puro e disposto a salire alle stelle.Thus with that same lilting word closes the epic’s second book, finished per-

haps four or five years after the first. The third book, Paradiso, is the journeyinto heaven, through the concentric spheres that (in the cosmic picture accept-ed from ancient times until three centuries after Dante) revolve around stolidEarth: first that of the Moon, where live the souls whose virtue waxes and wanes;on up to the other symbolic planets including (between Venus and Mars) theSun, to the eighth sphere, of the stars and saints, and the ninth, of the angels—this sphere is the Primum Mobile, which is turned by God and causes the lowerspheres to turn like cogs. And finally beyond physical space to the Empyrean, arealm of light which makes Beatrice more beautiful than ever and which revealsto him the mystery of the Trinity; he feels himself turned like a smooth wheel,along with the cosmos, by “the love that moves the Sun and the other stars”—

l’amor che muove il sole e l’altre stelle.Thus ends the Paradiso, from whose beatific vision Dante returned to the

petty world of Italian politics where he was usually on the losing side and alwayswithout Beatrice.

cov13.qxd 22/10/2012 01:22 Page 2

ASTRONOMICAL CALENDAR2013

by

Guy Ottewell

Sponsored by

the Department of Physics, Furman University,Greenville, South Carolina

the Astronomical League9201 Ward Parkway, Suite 100, Kansas City, MO 64114

816-DEEP-SKY www.astroleague.org

Universal Workshopwww.UniversalWorkshop.com

frontmat.qxd 22/10/2012 01:36 Page 1

Copyright © 2012 by Guy Ottewell. Printed in the United States of America. All rights reserved. Parts may bereproduced with prior permission and with acknowledgment.

ISBN 978-0-934546-62-1 ISSN 1051-6174

The first small issue of this annual book was for the year 1974. It had an unexpected boost from a comet (whichwas one of five discovered by Luboš Kohoutek and became unfairly notorious as a “disappointment”). This 40thissue had to include, at almost the last moment before printing, a comet that we think will not disappoint (seepage 67 and several others).

Sun Mon Tue Wed Thu Fri Sat2012

Julian Date at1.0 of month

12455927.5 2 3 4 5 6 78 9 10 11 12 13 14

15 16January 17 18 19 20 2122 23 24 25 26 27 2829 30 31 12455958.5 2 3 45 6 7 8 9 10 11

12 13 14 15 16February 17 1819 20 21 22 23 24 2526 27 28 29 12455987.5 2 34 5 6 7 8 9 10

11 12 13 14 15 16March 1718 19 20 21 22 23 2425 26 27 28 29 30 3112456018.5 2 3 4 5 6 78 9 10 11 12 13 14

15 16April 17 18 19 20 2122 23 24 25 26 27 2829 30 12456048.5 2 3 4 56 7 8 9 10 11 12

13 14 15 16May 17 18 1920 21 22 23 24 25 2627 28 29 30 31 12456079.5 23 4 5 6 7 8 9

10 11 12 13 14 15 16June17 18 19 20 21 22 2324 25 26 27 28 29 3012456109.5 2 3 4 5 6 78 9 10 11 12 13 14

15 16July 17 18 19 20 2122 23 24 25 26 27 2829 30 31 12456140.5 2 3 45 6 7 8 9 10 11

12 13 14 15 16August 17 1819 20 21 22 23 24 2526 27 28 29 30 31 12456171.5

2 3 4 5 6 7 89 10 11 12 13 14 15

16September 17 18 19 20 21 2223 24 25 26 27 28 2930 12456201.5 2 3 4 5 67 8 9 10 11 12 13

14 15 16October 17 18 19 2021 22 23 24 25 26 2728 29 30 31 12456232.5 2 34 5 6 7 8 9 10

11 12 13 14 15 16November 1718 19 20 21 22 23 2425 26 27 28 29 30 12456262.5

2 3 4 5 6 7 89 10 11 12 13 14 15

16December 17 18 19 20 21 2223 24 25 26 27 28 2930 31 12456293.5

For information about these and more, see

www.UniversalWorkshop.com

Where? What parts of the book are valid for what parts of the Earth?On the monthly pages, the Sky Maps and (usually) the horizon scenes are drawn for a mid-eastern American

location (latitude 40° north, longitude 70° west—roughly, Philadelphia). Differences across North Americaare small. For differing longitudes (such as California or Europe) the noticeable difference is in positions of theMoon. For latitudes farther south, more southerly stars come into view (see the fuller EXPLANATION OF THE MAIN

FEATURES). Most else is valid for anywhere on Earth.On the monthly pages, instants of events are given in Universal Time (the time for longitude 0), with trans-

lations for the Eastern time zone of North America. For many events, the exact time may be when the bodiesconcerned are below your horizon, but they will not have moved much a few hours earlier or later. Their visi-bility will be affected by their elongation (angular distance from the Sun).

From northerly latitudes such as North America and Europe, moving bodies such as planets and comets are,like stars, less easily visible when farther south, not visible at all if south of 90 degrees minus your latitude; andvice versa. For instance planets close to the Sun are affected by whether they are positioned north or south ofit along the ecliptic. This makes MERCURY much more often visible from the southern hemisphere (see theexplanation in that section).

Other phenomena most affected by time and your position on Earth are eclipses, occultations, and thepeaks of meteor showers.

Universal WorkshopP.O. Box 102, Raynham, MA 02767-0102, U.S.A.

800-533-5083 (toll-free) 508-802-5660 fax [email protected]

author: [email protected]

Darker blue means less moonlight in the following night.

About the contributing writers:

Fred Schaaf is author of 12 books (and co-author with Guy of Mankind’s Comet). A new, slightly revised editionof his book Seeing the Sky is now available from Dover Publications. He has written the stars and planets columnsin Sky & Telescope magazine for 20 years; been a light-pollution activist for over 30; written a weekly newspapercolumn on astronomy for over 35 years. He teaches at Rowan University in Glassboro, N.J. Information on theInternational Decade of the Sky by Fred Schaaf will this year be available at www.UniversalWorkshop.com/DecadeOfTheSky

Clifford Cunningham has written or edited 11 books, and is a contributing editor to Mercury magazine. In 1990,asteroid 4276 Clifford was named in his honour, and in 1999 he appeared as a Starf leet officer in an episode of“Star Trek: Deep Space Nine.” He is currently in the PhD astronomy program at James Cook University inAustralia.

Alastair McBeath, a British observational astronomer, has been a leader in the International MeteorOrganization and in the Society for Popular Astronomy. Among some hundreds of his publications are bookson observing and on mythology. Along with Andrei Dorian Gheorghe of Romania, he set up the Meteor BeliefsProject (www.imo.net/projects/beliefs).

Alan Hale, a long-time comet observer, discovered Comet Hale-Bopp in 1995. He is author of a book about it,as well as research papers and articles. He led two American delegations on visits to Iran, and founded Earthrise,a project that fosters international scientific collaboration. He teaches university-level classes in astronomy andspace studies.

Joe Rao is a television meteorologist in New York’s Hudson Valley. He has co-led eclipse expeditions and beenon-board meteorologist for eclipse cruises; is a lecturer at New York’s Hayden Planetarium; and contributes toSky & Telescope, Natural History, The New York Times, The Farmers’ Almanac, and Space.com.

Richard Nugent worked at NASA’s space center in Houston, Texas, analyzed imagery from the LANDSAT satellites,and made real-time calculations of orbits and rendezvous maneuvers for the Space Shuttle. He is executive sec-retary of the International Occultation Timing Association (IOTA), wrote its observing manual, has over 60 pub-lications, and has traveled on over 120 scientific expeditions involving occultations and eclipses.

All illustrations and their captions are by Guy Ottewell, except for maps drawn by Richard Nugent for his“Occultations” section.

John Goss, Astronomical League Vice President, has very kindly proof-read most sections of this book as theywere completed. As a result, this is probably the first issue of the Astronomical Calendar not needing a subsequentlist of errors. I should have accepted his offer when he started making it three years earlier.

Some other publications by Guy Ottewell:

The Astronomical CompanionGeneral guide to astronomy (not annual), with many 3-D diagrams

Albedo to ZodiacGlossary of astronomical terms, with pronunciation, origin, meaning

To Know the StarsChildren’s introduction to astronomy

The Thousand-Yard Model, or, The Earth as a PeppercornInstructions for a walk making vivid the scale of the solar system

The Under-Standing of EclipsesThe geometry, history, and beauty of eclipses

Berenice’s HairStory of the stolen tress that became the constellation Coma Berenices.The novel climaxes (like the year 2013) with a daylight comet!

The Troy Town TaleThe whole legend of Troy, in the form of a novel

Portrait of a MillionPoster conveying the concept of a million, with million-facts

American Indian Map, and Navajo MapThe Arithmetic of VotingLanguage (poems)Plurry: a musical instrumentThe Spiral LibraryStripe Latin: a grammar gameTen-Minute History of the World; and, Queen Guinevere’s RulesThink Like a Mother: a photo book of human rightsTurkey, A Very Short HistoryThe Winged Velocipede; or, how to f ly overseas with your bicycle

This will be the last Astronomical Calendar in the present format. To learn about the plan for futurepublication, please visit www.UniversalWorkshop.com or email [email protected].


Astronomical Calendar 2013 3

FOR THE BEGINNER—TEACH YOURSELF ASTRONOMY WITH THIS CALENDAR

When you first look at a page of this book, it may seem frighteningly tech-nical. That is because a lot of information has been packed in, for the moreadvanced astronomer. You may be surprised at how soon you come todemand this information yourself. But, to begin, the key is selection.

What to concentrate on at first. Ignore everything but the sky map for thepresent month. Read just the first part of the sky map explanation, lowerdown this page. In the sky map, ignore everything but the constellations—the star pictures, such as “ORION” or “CYGNUS.” And, of these, ignore allbut the conspicuous constellations—those in which the connecting lineshave been drawn thick.

During the month, learn just two or three of those conspicuous constel-lations that are near the middle of the map. For example, on an evening inJanuary learn the shape (not the other details) of Orion, and build outwardfrom him to Taurus and Auriga. On the next evening, or soon after, checkthat you have remembered these. In February, build from them to CanisMajor and Gemini.

This, of course, is only an example of procedure. You will work in yourown way, and you can easily work a lot faster.

The difficult part is not the shapes of the constellations: it is the relationsbetween them. For example, how much gap is there between Taurus andGemini, and which horn of Taurus points to which foot of Gemini? The bestway is to keep drawing sketches from memory, then checking them by thesky or the map.

Hints toward remembering constellations, and connecting them witheach other, are given in the “Constellation Clues” above each sky map.

If you learn just a little from the middle of the sky each month, in a yearyou will have memorized a framework of constellations completely encir-cling the sky back to where you started.

Not “how to go on” but “how you will find yourself going on.” Having aframework is the turning-point. Before you have a framework, you can hard-ly do anything with a new fact; after you have a framework, you can hardlyhelp accumulating facts in it. You will find yourself looking at the map forthe names of the brighter individual stars you have learned—Betelgeuse,Sirius, Vega—and soon regarding them as old friends. You will fiind your-self filling the gaps between conspicuous constellations with dimmer ones.Knowing the constellations, you will know when you are looking at a plan-et, for the main way of recognizing planets is that they are “stars” where nostar should be in the constellation pattern. You will find yourself ready tounderstand the other features of the maps (numbers, lines) and other partsof the book. You will find yourself tempted out to see some of the eventsmentioned in the list, such as the Perseid meteor-shower in August, or a pat-tern formed by Venus, Mercury, and the Moon. You will find yourself look-ing at the other pages for explanations as you need them.

And you will probably become curious about the colors, distances, andphysical nature of the stars. You will find yourself seeking other books, andreading with enlightenment the latest news of scientists’ discoveries aboutthe universe.

By using this Calendar intermittently through the year, you will have har-nessed the seasons to give yourself a rather effortless and comprehensivecourse in astronomy.

EXPLANATION OF THE MAIN FEATURES

The time for which the maps are drawn is, more closely, about 10 p.m. local time around the5th of the month, or about 9 p.m. local time around the 20th of the month.

The time on your clock can be as much as half an hour before or an hour and a half afteryour true local time, because of standard time-zones and changed summer time. To find outwhat exactly the difference is, use the Personal Reminder (inside back cover). More expla-nation is in the Astronomical Companion, section on TIME.

Stars are shown down to magnitude 4.7, plus about 40 fainter ones which, in the barerparts of the sky, have come to seem necessary. (An example is Eta Ursae Minoris, joiningthe Little Dipper’s handle to its pan.) So all the stars are visible (if the sky is dark and clear)to the naked eye, for which the limit is about magnitude 5 or 6 (see the MAGNITUDE graph).

Some deep-sky objects—clusters, nebulae, and galaxies—are marked. Those with “M”numbers are in the famous 18th-century catalogue by Charles Messier.

Constellation forms (skeletons, we might call them) are expressed by lines from star tostar—curving lines, unlike in most other books. These ways of seeing the constellations aretraditional, but can be modified by personal custom. The aim here is to make them both per-ceivable in the real sky (thus it is no use including stars too dim for ordinary conditions, ordrawing too many ingenious lines between non-adjacent stars in order to make recognizablepictures on paper) and learnable (in this, symmetry and other kinds of regularity help). Thicklines mark conspicuous constellations. The others—and the lesser parts of some constella-tions, such as the sword, club, head, and upraised lion-skin of Orion—can be left for learn-ing later.

In a few places the form-lines are dashed: b Tauri is also felt to be part of Auriga; aAndromedae is a corner of the Great Square of Pegasus.

To avoid overcrowding these maps, much detail is left out, and given instead in theCENTERFOLD MAPS, which are for the entire sky at no particular time: constellation bound-aries, more star-names, Greek-letter star designations, star colors (spectral types), and moredeep-sky objects.

The stars and deep-sky objects are a fixed background. As they look on a Januaryevening this year, so they will look next year, or indeed next century, except for smallchanges by precession, and even smaller changes by proper motion (see the .

In front of them is a moving foreground, consisting of everything inside our solar system:planets (including the minor planets or asteroids), comets, the Sun, the Moon, and, movingfaster than all these because it is even nearer, the horizon of our own Earth. Faster still,because nearer, are artificial satellites, then meteors and other phenomena inside the Earth’satmosphere.

If a planet is above the horizon at this time, it is shown with a symbol at its position onthe 15th of the month. The symbols are sized for brightness like the stars, but asterisk-shapedinstead of circular. An arrow shows the movement during the month. Planets are visible tothe naked eye, except Uranus (theoretically visible but very difficult), Neptune, and Pluto.

Remember that these maps are of the mid-evening sky: there are other groupings of plan-ets in the early-evening sky just after sunset, and in the sky after midnight. Mercury in par-ticular cannot appear except close to sunset or sunrise. The mid-evening maps cannot indi-cate these groupings; you can watch for them in the book’s other diagrams.

The Moon is shown (exaggerated 6 times in size) at 0h (midnight) at the start of each dayby Universal (Greenwich) Time. This is 7 p.m. of the previous day by Eastern Standard Time,4 p.m. by Pacific Time, etc. (Up to Ast.Cal. 2008 it was shown at 10 p.m. Eastern StandardTime, which is 3 in the morning of the following U.T. day. Either way can be confusing.) Itis shown in its geocentric position, that is, without parallax, which would push it slightlysouth. It is marked “first quarter” or “full” when it is nearest to these exact phases.

Some of the major meteor showers are indicated by a burst of lines pointing away fromthe radiant in the constellation from which the meteors radiate and from which they receivetheir name: the Quadrantids in January, Lyrids in April, Perseids in August, and Geminids andUrsids in December. (But the Eta Aquarids of May, Orionids of October, and Leonids ofNovember cannot be shown here because their radiants have not risen into view at maptime.)

These solar-system features (except the meteor showers) are what change position fromyear to year. Thus the January sky-map will be valid for January of the next year too—exceptthat the planets and Moon will be in different places.

The January sky-map is also valid for two hours earlier on a February evening, and so on.(See the note at bottom right of each map.) Thus, though we give maps for mid-evening only,

The Sky DomesEach map represents the whole of the sky that you can see, at the conve-nient time for viewing in the evening.

It is a map of a dome. That is why the horizon, which we tend to thinkof as a straight line, has to be here a circle. Imagine the black dome bulgingdownward into the paper.

But the ideal way to understand asky map is to go outside after dark, lieon your back (or on a long chair)with your feet pointing south, andhold the map over your face.

It will now be easy to see the rela-tion between map and sky. The cen-tral point of the map is the zenith.This is the point overhead, in the middle of the sky, the point you should becovering with the map. The circular edge of the map is the horizon that sur-rounds you. At the bottom edge of the map is the word “south,” corre-sponding to the southern part of the horizon in front of you.

Since you are facing south, east is to your left and west to your right. And

these directions are shown at the left and right sides of the map respective-ly. This explains why east is at the left of a celestial (sky) map whereas it isat the right of a terrestrial (Earth) map. An Earth map is a view down; a skymap is a view up.

Having thoroughly understood this, you can study the sky maps in theusual looking-down way—on a table or your lap—so long as you keepreminding yourself that they represent a view up.

When instead of facing south you face east, turn the book so that theeastern horizon is at the bottom edge of the map. Similarly for west andnorth. This way, you will keep the map “set,” so that what is left, above, etc.in the sky corresponds to points arranged the same way in the map.

The “rising” and “setting” arrows at the edges show the distances thatpoints in the sky move in one hour. Stars are slowly coming up on the east,passing overhead, and going down in the west. Watch for long enough toconvince yourself that this is really so.

Turn the pages: you will see that the January, February, etc., mapsbecome a “movie” of the sky slowly turning, pivoted at Polaris, the almostunmoving North Pole Star. The sky makes this turning-motion (1) from hourto hour through any one night, (2) from month to month, if we select thesame time to look each month. (See the note at bottom right of each map.)

Technical terms of astronomy are explained in our glossary Albedo to Zodiac. vg



The Solar System PlansEach of these is a view of the solar system from above—thatis, from outside it in space to the north. Each shows theprogress of the planets (including our Earth) around the Sunin the course of the month.

Only the four inner planets are shown. The orbits of theouter four get farther apart at an increasing rate; to showthem, the scale would have to be reduced so much that theMars-and-inward part, where most of the phenomena hap-pen, would shrink to a dot half a centimeter wide! Anyway,the outer planets change their positions little, because the far-ther out they are the slower they move. Lines point off thesides of each diagram to their directions from the Sun at themonth’s beginning and end. Jupiter this year moves 31.214°around the circle; Saturn, 11.484°; Uranus, 3.934°; andNeptune, 2.206°. Pluto moves on average 1.45°, but, beingstill on the inner part of its eccentric orbit, was progressingslightly faster than Neptune till 2006, and has now slowed to1.988° in the year.

The courses of the four inner planets for the month arerepresented by curving arrows. Where a planet is on orabove the ecliptic plane (plane of the Earth’s orbit) its line isthicker.

The rest of each orbit is indicated by dots, 5 days apart inthe planet’s motion. Thus the spacing of the dots shows therelative rapidity of Mercury and slowness of Mars. The dotsare black for the part of its course that a planet has troddensince the beginning of the year; blue for the rest. Thus youcan see in June, for instance, that Earth is now half wayaround, Mars only a quarter, and Mercury is repeating itself.

These orbital tracks are not circles, but slightly off-centerellipses. This is particularly noticeable for Mercury and Mars.But Earth, too, is 5 million kilometers nearer to the Sun at per-ihelion (in January) than at aphelion (in July). Venus’s orbit isthe closest to circular.

The white side of the diagram represents your outlookinto space at about 10 p.m. in the middle of the month (actu-ally, it assumes that you are on the equator). The linebetween white and gray is the horizon at that time; the grayis the half of the universe below ground-level, including theSun. By local midnight, you are looking straight outward: thehorizon-line is tangent to the Earth’s orbit. As the night goeson, the horizon rotates counterclockwise, until the Sun isagain uncovered.

The Moon’s position when it is new (on the inner side ofthe Earth’s curve) or full (on the outer side) is shown by asmall semicircle representing its sunlit half. Its distance fromEarth is vastly exaggerated, its size still more. “New Moon”means when the Moon is exactly Sunward from the Earth;“full,” when it is exactly on the opposite side, showing us itssunlit face. It weaves from one of these positions to theother, crossing the Earth line at first quarter (when it has fall-en behind the Earth) and last quarter (when it has movedahead).

Eclipses are shown by a schematic shadow falling fromEarth onto Moon (at a lunar eclipse) or Moon to Earth (solareclipse).

Solstices and equinoxes of the Earth are represented byshort lines across its orbit.

The Sun’s north pole, leaning maximally away from theEarth in March and toward it in September: a short line fromthe Sun.

Opposition of a planet: a solid line from the Earth outtoward it. (We might draw the line all the way from Sunthrough Earth to planet, but this would clutter the diagram.)

Maximum elongation of Mercury or Venus east or westfrom the Sun: a thinner line from Earth to planet.

Conjunction with the Sun: a dotted line from planet toSun (it might continue to the Earth).

Conjunction of two planets: a dashed line betweenthem (or toward the outer planet, if it is off the picture; theline might continue to the Earth).

Perihelion and aphelion: ticks, respectively inward andoutward, from a planet’s orbit.

Ascending node is where a planet’s curve changes fromthin to thick; descending, from thick to thin. Greatest lati-tudes north and south (not marked) are half way betweenthese nodes.

(Perihelion, aphelion, nodes, and greatest latitudes areheliocentric events, i.e. in relation to the Sun; conjunctions,oppositions, and elongations are geocentric, i.e., seen fromEarth.)

Since the diagrams are on flat paper, everything in themhas to be projected onto one plane. It is the plane of theecliptic—that is, of the Earth’s orbit. The other bodies shouldrise and fall from this plane, but only slightly. Thus Mars at itsgreatest latitude north should be 1½ millimeters above thepaper (that is the greatest such difference). Orbits projectedonto the plane of the ecliptic are called curtate orbits (“short-ened”). The only orbits departing much from the generalsolar-system plane are those of some asteroids, Pluto andother Transneptunians, and many comets and meteors.

(Besides the ecliptic plane, which is derived from themotion of our own planet only, there is the “invariant planeof the solar system,” defined by taking into account all theplanets’ orbital planes and masses. It differs by only 1.65°from the ecliptic plane, and is almost identical with Jupiter’s.)

Because the diagrams are projected on the ecliptic plane,conjunctions are shown as they happen in longitude (that is,angular position around the ecliptic), not in right ascension oras appulses. Usually this makes little difference, but an eventinvolving Mercury or Pluto could, because of their inclinedorbits, be shown on a date noticeably different from that list-ed in the calendar.

It is good, at each event mentioned on the facing page,to see how it corresponds with the diagram. For instance, ata conjunction of Mercury and Venus (“Mercury 4° south ofVenus”) look from the Earth along the line connectingMercury and Venus.

Major meteor streams (such as the Quadrantids inJanuary) are shown as blue paths (darker when north of theecliptic plane) along the parts of their orbits 60 days beforeand after their perihelia.

The scale (shown by a scale-line on the January diagram)is about 2.8 centimeters to 1 astronomical unit (the average

Sun-Earth distance, about 150 million kilometers or 93 millionmiles). Hence, 1 millimeter represents 5.39 million km. Sucha scale cannot possibly be kept true for the sizes of the bod-ies. The Sun ought to be about ¼ millimeter wide. The Earthis more than a hundred times smaller, so at true scale it wouldbe deeply invisible. Even the distance of the Moon from theEarth is little more than half the true radius of the Sun, thusonly 0.07 millimeter in our diagram! This shows that theMoon’s real orbit is virtually the same circle as the Earth’s.

Around the edge of each diagram are the zodiacal constel-lations. You can read off from the diagram the constellations“in” which the Sun and planets appear, and “in” which con-junctions and other events occur.

Some things may puzzle you about the way the constel-lations are shown:

(1) Why are they various in width? Because, in modernastronomical maps, definite boundaries have been drawnaround the parts of the sky traditionally felt to be in each con-stellation; these areas are irregular and vary in size and shape;and what we are showing are the points where the eclipticcrosses these boundaries.

(2) Why is there a 13th constellation, Ophiuchus, notbelonging to the traditional zodiac? The constellation bound-aries have been fixed in such a way that the Sun actually trav-els through a part of this constellation. This is a time of theyear when the Sun is loosely “in Scorpius,” but in fact mostof that constellation lies south of the ecliptic. (The part ofScorpius that the Sun actually traverses is so narrow that Ihave to compress the name to “Sco.”)

(3) Why do the constellations shift to and fro around theedges of the diagrams? Because we are showing them asdirections from the Earth (at the middle of each month), notfrom the Sun.

The stars making up the constellations do not move. Allstars are at virtually infinite distance, compared with anythingin the solar system. (On the scale of the diagrams, the near-est star would be 7 kilometers or 5 miles away!) So the direc-tion to any star from Earth is virtually the same as that fromthe Sun. (The difference is the extremely small angle calledthe star’s parallax.)

(4) Why does a line representing the position of a planetsometimes seem to point into Taurus when the planet is actu-ally in Gemini? Again, because these lines are in relation tothe Sun, whereas the constellation boundaries point awayfrom the position of the Earth. You will see that a line paral-lel, but drawn from the position of the Earth, would lead out-ward into the correct constellation. If you want to knowexactly in what part of what constellation an event (repre-sented by a line) occurs, draw a line parallel to it from theEarth’s mid-month position.

To see what the solar system diagram means for us at ourviewpoint on the Earth: get your eye almost to the plane ofthe paper (such as by lifting the book horizontally to youreye-level) and look past the Earth symbol to the backgroundbeyond it. You will see whether, for example, Venus is to theright or left of the Sun, and whether it is moving against thebackground of Sagittarius or Capricornus.

Horizon ScenesDiagrams on the timetable pages show the horizon-based view of parts of the sky at select-ed dates. They are evening and morning twilight scenes, at times shortly after sunset orbefore sunrise. You can infer the scene an hour later, or half an hour earlier, etc., from thearrow showing how the sky rotates in one hour.

These drawings are on the altazimuth system: that is, the up-down dimension representsaltitude from the horizon, and the left-right dimension represents azimuth along the horizon.There is distortion (left-right stretching) at high altitudes, where the dome of the sky shouldclose together toward the zenith.

The drawings are at a scale of 2 millimeters per degree—except for the Feb. 6 and May27 ones, which are at a scale twice as large. The scale can be seen in the measures of alti-tude at the side. Also, the ticks along the horizon are 5° apart, and the compass directions(W=west, NW=northwest, etc.) are 45° apart.

The celestial equator is shown as a line with tick-marks one hour of right ascension (15°)apart; the ecliptic as a broader line. The position of the Milky Way is indicated in the back-ground (giving a sense of which part of the universe we are looking toward), though it willnot be visible in twilight.

A few bright stars are shown, and the Pleiades and Beehive clusters (though they will bebelow visibility when low in a twilight sky); and the major planets and Pluto (though Uranus,Neptune, and Pluto are fainter than thousands of stars not shown and cannot be seen withthe naked eye). The Sun’s position is shown below the horizon, and the Moon and planetstoo, because this serves to remind you that for instance Mercury has just passed out of theevening sky, or is about to move up into it.

The circle for the Sun (which is always on the ecliptic), and the illuminated part of theMoon, are drawn 2 times larger than scale. This can make them appear to occult (get in frontof) stars and planets more often than they really do.

From day to day the Sun moves eastward roughly 1° on the ecliptic. (The position of thehorizon, therefore, at the corresponding time of day moves by the same amount.) As for theplanets, their apparent movement is eastward (leftward) most of the time, but westward dur-ing their retrograde times, when they are nearest to us. Mercury and Venus move sometimesfaster than the Sun, sometimes slower; the other planets always slower. To suggest the direc-tion of change between our scene and the neighboring days, we add for the Sun and eachplanet an arrow showing its movement from its position 2 days ago to its position 2 daysahead—that is, its real position, against the starry background. To find a planet’s altazimuthposition (its position relative to the horizon) you have to subtract the Sun’s motion; thus aplanet moving left (east) on the map of the sky will, if its motion is less than the Sun’s, be seenslightly farther right (west) in relation to the horizon at the same time of the next day.

The Moon moves far faster than all these: 13° east per day on average (more if it is in anear part of its orbit, less if it is far). We show it at the same time on several preceding and

following days. (Its position, being in relation to the stars, cannot be quite exact in relation tothe moving planets.) This emphasizes the Moon’s flying motion, and shows as many as prac-ticable of the numerous Moon-planet and Moon-star conjunctions. If you cannot identifyJupiter, for example, any other way, a sure way is to look on an occasion when it is the bright“star” near the Moon.

The pictures are drawn for the eastern U.S.A. (latitude 40° north, longitude 75° west), butgive an idea of what is seen from anywhere in the north temperate zone of the Earth. If youare at a different longitude, the only serious difference will be for our fast-moving satellite theMoon. For example if you are on the West Coast, about 45° of longitude or 3 time-zones tothe west, sunset comes to you 3 hours later; the Moon will by then have progressed 3/24 ofthe way toward its next-day position.

Differing latitude, also, affects the Moon, which is plotted taking into account local paral-lax (its displacement as seen from the particular location on the surface of the Earth, insteadof from the Earth’s center). This is why the Moon may be shown passing south of a star orplanet on a date when the calendar says it (that is, its center) passes north. If you live farthernorth, the Moon will appear still farther south in the sky; if you are in the southern hemi-sphere, the Moon will instead appear north of its geocentric position. The arrows showingthe Moon’s motion lie farther north than the Moon images: that is because the points onthem have to be calculated for different times of day and therefore without parallax. Hencethey give an idea of where the Moon would appear if seen from the center of the Earth.

Latitude also affects the picture more generally. As you go farther north, the celestialequator arches at a lower angle, with less sky under it; till, at the north pole, the equator ispressed flat, becoming one with the horizon. Conversely, if you go south, the equator slopesup more steeply; till, as seen from the terrestrial equator, it stands vertically from the east andwest points to the zenith. For the southern hemisphere, it leans the other way (rightward fromthe west, or evening, horizon, and leftward from the east point).

Times are given in relation to sunrise or sunset; also in Eastern clock time (EasternStandard Time in winter, Eastern “Daylight-Saving” Time in summer), since the scenes are asfrom the middle of the Eastern time-zone; also in Universal (Greenwich) Time, which is 5hours after EST, 4 hours after EDT. The scenes will not be appreciably different (except forthe Moon) at the same clock time in other time-zones.

Bodies are generally unobservable if closer to the Sun than about 10°, or to the horizonthan about 5° (unless very bright, like Venus and the Moon). So in some cases the picturesmerely tell you why you cannot hope to see the bodies—though, when the reason is thatthey are well south of the celestial equator, they will appear high for people in the southernhemisphere. But all are of interest: you can use the sky maps opposite to keep you aware ofwhat is happening in the night sky, and the horizon scenes to keep you aware of what is hap-pening in twilight—in the part of the sky that sets before darkness comes. Following thescenes from month to month you can see the evolving relationships of the solar-system bod-ies as they move along near the ecliptic.


For latitude 40° northand sidereal time

11h

Apr. map serves forMay 7–8 p.m.June 5–6

Dec. 5–6 a.m.Jan. 3–4Feb. 1–2Mar. 11–12 p.m.

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12 Astronomical Calendar 2013

APRIL Aprilis, month of opening (aperture)or, according to the Romans, of thegoddess Aphrodite (Venus)

telescopic tour(coordinates of 2000)

2 21.5 +57 08 Perseus double cluster2 29.0 +67 24 ι Cassiopeiae, triple star2 50.6 +55 53 η Persei, double star6 08.9 +24 21 M35 cluster7 34.6 +31 54 Castor, double star8 40.4 +19 41 Praesepe cluster9 55.6 +69 04 M81 galaxy

10 19.9 +19 51 γ Leonis, double star12 24.5 +25 43 Coma Berenices cluster12 30.8 +12 23 M87 galaxy12 36.4 +25 59 NGC 4565, Spindle galaxy

12 41.7 —1 26 γ Virginis, double star12 56.1 +38 19 Cor Caroli, double star12 56.8 +21 41 M64, Blackeye galaxy13 23.9 +54 55 Mizar, double star13 29.9 +47 12 M51, Whirlpool galaxy13 42.2 +28 23 M3 globular cluster15 18.5 +2 05 M5 globular cluster16 41.7 +36 27 M13 globular cluster17 32.2 +55 11 ν Draconis, double star17 41.9 +72 10 ψ Draconis, double star

constellation cluesLeo is one of the few constella-tions that look like what they aresupposed to be.

Crater (the “goblet”) is another.West end of Leo (Regulus hisheart, Algieba his shoulder, and3 more for his mane and head):also called the Sickle. Could bea backwards question mark.

East end of Leo: a triangle.Denebola, “tail of the (lion),”was anciently a first-magnitudestar, brighter than Regulus.

Merak and Dubhe point toPolaris; the distance is 5 timestheir separation.

They point back the other way toLeo.

Layers:Ursa MajorLeo Minor

LeoHydra

Sky Domeabout 10 p.m. at the 5th of the month

or 9 p.m. at the 20th

for:5–6 p.m.7–8

11–121–2 a.m.3–45–6

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months.qxd 22/10/2012 01:46 Page 12

For latitude 40° northand sidereal time

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Jan. 5–6 a.m.Feb. 3–4Mar. 1–2Apr. 11–12 p.m.

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perihelionperihelionnodenodeconjunction with Sunconjunction with Sunconjunction of planetsconjunction of planets (in longitude) (in longitude)


MAY Maius, month of the goddess Maia,or of the elders (maiores),or of growth

telescopic tour(coordinates of 2000)

13 26.7 —47 18 ω Centauri globular cluster2 29.0 +67 24 ι Cassiopeiae, triple star7 34.6 +31 54 Castor, double star8 40.4 +19 41 Praesepe cluster9 55.6 +69 04 M81 galaxy

10 19.9 +19 51 γ Leonis, double star11 14.7 +55 01 M97, Owl nebula12 30.8 +12 23 M87 galaxy12 40.0 —11 36 M104, Sombrero galaxy12 41.7 —1 26 γ Virginis, double star

14 45.0 +27 04 ε Boötis, double star15 18.5 +2 05 M5 globular cluster15 39.4 +36 38 ζ Coronae Borealis, double star16 41.7 +36 27 M13 globular cluster17 14.7 +14 24 α Herculis, double star17 32.2 +55 11 ν Draconis, double star17 41.9 +72 10 ψ Draconis, double star18 44.4 +39 40 ε Lyrae, double-double star19 30.7 +27 58 Albireo, double star

constellation cluesComa was once a tuft on theLion’s tail; flattering priests thenpretended it was QueenBerenice’s hair.

Coma is a cluster of stars, and farbeyond it a cluster of galaxies.

The richest area in the sky forgalaxies extends from UrsaMajor down through Coma intoVirgo.

Virgo: a somewhat shapelessMaiden.

Spica is an “ear of wheat” she isholding in her left hand.

Hydra continues, under the littleconstellations of the Sextant, theCup (Crater), and the Crow(Corvus).

Sky Domeabout 10 p.m. at the 5th of the month

or 9 p.m. at the 20th

for:5–6 p.m.7–8

11–121–2 a.m.3–45–6

see map for:March

April

JuneJuly

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Deneb

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14

May

14

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Moon

1515

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1818firs

tfirs

t

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r

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September

± 1 SUN. Aurigids. See METEORS. Very favorable year for this usually minor shower.( 9 UT= 5 EDT) The equation of time is 0. See Feb. 11.(10 UT= 6 EDT) Moon 11.5° S.S.W. of Pollux (46° from Sun in morning sky).

± 2 Mon. ( 5 UT= 1 EDT) Moon 6.1° S.S.W. of Mars (about 37° from Sun in morning sky).(16 UT=12 EDT) Moon 6.4° S. of Beehive Cluster (33° from Sun in morning sky).

² 4 Wed. (11 UT= 7 EDT) Moon 5.2° S.S.W. of Regulus (only about 12° from the Sun).² 5 Thu. Rosh Hashanah, first day of the Jewish year 5774 A.M. The Jewish day begins at

the previous sunset, traditionally when the sky is dark enough for three stars to beseen. The new-year sunset is that of the young Moon’s appearance closest to theautumn equinox. (The date is calculated, with formulae established by Hillel II in 363A.D., from the Moon’s mean motion, and is occasionally one day too early, as in2002.)

(11:35 UT= 7:35 EDT) � Moon new. Beginning of lunation 1122.² 6 Fri. ( 4 UT= 0 EDT) Venus 1.6° N.N.E. of Spica (40° from Sun in evening sky); mag-

nitudes —4.0 and 1.0. Conjunction in r.a. is 15 hours earlier.(10 UT= 6 EDT) Moon 4.5° S.S.W. of Mercury (only about 11° from the Sun).

_____________________________________________________weeks____________± 8 SUN. Sun’s north pole most inclined (7.25°) toward Earth. See March 6, and SUN.

(15 UT=11 EDT) Moon, Venus, and Spica within circle of diameter 3.27°; 32°East of the Sun.

(16 UT=12 EDT) Moon 1.1° E.N.E. of Spica (about 38° from Sun in evening sky).Occultation.

(22 UT=18 EDT) Mars 0.23° S. of the center of the Beehive Cluster (39° fromSun in morning sky). Conjunction in r.a. is 1.5 hours later.

(22 UT=18 EDT) Moon 0.76° S.E. of Venus (about 41° from Sun in evening sky).Occultation.

± 9 Mon. September Epsilon Perseids. See METEORS. Very favorable year for this usuallyminor shower.

(17:29 UT=13:29 EDT) Moon at ascending node (longitude 218.8°).(18 UT=14 EDT) Moon 2.5° S. of Saturn (about 51° from Sun in evening sky).(21 UT=17 EDT) C/2012 F6 Lemmon at opposition. See COMETS.

± 11 Wed. (23 UT=19 EDT) Moon 7.2° N. of Antares (about 80° from Sun in evening sky).± 12 Thu. (17:09 UT=13:09 EDT) � Moon at first quarter.° 13 Fri. Friday the 13th—supposed to be very unlucky because both the day and the

number are unlucky. (In South America the unlucky day is Tuesday and in Italy theunlucky number is 17. In Iran women stay outdoors on the 13th day of the year toavoid bad luck.) This year has two Fridays-the-13th: see Dec. They occur every year,either once or twice (each in 42-44 years per century) or 3 times (14 or 15 years percentury: common years beginning with Thursday, such as 1981, 1987, 1998, 2009,and 2015, when, occurring in February, it must also occur in March; or, most rarely ofall, leap-years beginning with Sunday, such as 1984, 2012, 2040, 2068, 2096, 2108).

Actually, Friday falls on the 13th more often than any other day does! (BecauseSunday most often falls on the 1st.) In every span of 400 years after 1582 (beginningof the Gregorian calendar) the numbers of Sundays-the-13th, Mondays-the-13th etc.are: 687 685 685 687 684 688 684. —In some years, such as 2007 and 2013, twoFridays-13 are 13 weeks apart, and in 2012 all three were (as pointed out by JeanMeeus in his chapter on Friggatriskaidekaphobia, “Friday-thirteen-fear,” MathematicalAstronomy Morsels III, p. 365).

(11 UT= 7 EDT) 324 Bamberga at opposition. See ASTEROIDS.(20 UT=16 EDT) 1 Ceres at perihelion, 2.5515 a.u. from the Sun. See ASTEROIDS.

° 14 SAT. ( 1 UT=21 edt) Moon 1.5° N.N.W. of Pluto (107° from Sun in evening sky).(16 UT=12 EDT) Mercury at descending node through the ecliptic plane.

______________________________________________________________________° 15 SUN. (16 UT=12 EDT) Moon at perigee. Distance 57.60 earth-radii.° 16 Mon. (19 UT=15 EDT) �� Sun enters Virgo, at longitude 174.07° on the ecliptic.° 17 Tue. (21 UT=17 EDT) Moon 5.4° N.N.W. of Neptune (about 158° from Sun in

evening sky).� 18 Wed. (16 UT=12 EDT) Venus 3.5° S.S.W. of Saturn (43° from Sun in evening sky);

magnitudes —4.1 and 0.7. Conjunction in r.a. is 32 hours later.� 19 Thu. (11:12 UT= 7:12 EDT) � Moon full. See SPECIAL MOONS.� 20 Fri. ( 5 UT= 1 EDT) Pluto stationary in right ascension; resumes direct (eastward)

motion. The stationary moment in longitude is 12 hours later.(13 UT= 9 EDT) Moon 3.1° N.N.W. of Uranus (about 166° from Sun in morning

sky).______________________________________________________________________

° 22 SUN. (13:49 UT= 9:49 EDT) Moon at descending node (longitude 38.2°).(20:44 UT=16:44 EDT) Fall or autumn equinox. The Sun, appearing to travel

along the ecliptic, reaches the point where it crosses the equator into the southerncelestial hemisphere. Fuller description in Ast. Companion, SEASONS. Since 1968 thisequinox has fallen on Sep. 23 or 22; till 1931 it fell sometimes on Sep. 24.

Sun enters (at the equinox) the astrological sign Libra, i.e. its longitude is 180°.But astronomically it is still in Virgo. See Ast. Companion, PRECESSION.

° 24 Tue. ( 6 UT= 2 EDT) Moon 6.0° S. of Pleiades (about 121° from Sun in morning sky).° 25 Wed. ( 1 UT=21 edt) Mercury at aphelion, 0.4667 a.u. from the Sun.

( 1 UT=21 edt) Mercury 0.74° N.N.E. of Spica (22° from Sun in evening sky);magnitudes —0.1 and 1.0. The year’s closest approacj of a planet to a 1st-magnitudestar. Conjunction in r.a. is 6 hours earlier.

( 2 UT=22 edt) Moon 2.8° N.N.W. of Aldebaran (about 112° from Sun in morn-ing sky).

° 27 Fri. ( 3:55 UT=23:55 edt) � Moon at last quarter.( 5 UT= 1 EDT) Mars 2.0° south of C/2012 S1 ISON (about 45° from Sun in

morning sky); magnitudes 1.6 and 10. Mars doesn’t quite overtake ISON (there is con-junction in longitude and r.a. but no appulse) and ISON now speeds to overtakeMars—see Oct, 18.

(18 UT=14 EDT) Moon at apogee. Distance 63.39 earth-radii.± 28 SAT. ( 6 UT= 2 EDT) Moon 4.9° S.S.W. of Jupiter (about 77° from Sun in morning

sky).(19 UT=15 EDT) Moon 11.7° S. of Pollux (73° from Sun in morning sky).

______________________________________________________________________± 29 SUN. (23 UT=19 EDT) Moon 6.5° S.S.W. of Beehive Cluster (about 59° from Sun in

morning sky).

September is the month when visual discoveries of asteroids have tended to be most numer-ous—344 of the first 1,940 numbered asteroids, or more than twice the average. One reasonis that observers search mainly the part of the sky in opposition to the Sun (the midnight sky),and, for Europe, where asteroids have longest been hunted, the September midnight sky isPisces and its surrounding “watery” constellations: star-poor areas where asteroids are moreeasily detected. Also a maximum of asteroids have their perihelia in the Pisces direction nearecliptic longitude 13°, because that is the perihelion of Jupiter, which has been pulling theirorbits into alignment with its own. The months when fewest asteroids were discovered areJune (65 of the 1,940) and December (75); in both, the midnight sky is in the Milky Way(Sagittarius in June, Gemini in December). Also, in June the nights are short; in December,cold and overcast. In future, with searches made in other parts of the world and with automa-tion, the monthly distribution will tend to become even.

Observers’ highlights for September by Fred SchaafVenus passes first Spica and then Saturn in the evening sky,but more exciting is the Moon’s very close passage of Venus.Mars treks through M44, the Beehive Star Cluster, in themorning sky. Harvest Moon and possible major auroralactivity also are attractions. But the background to this all isthe approach, and brightening to maybe 10th magnitude, ofComet ISON, which Mars passes near in the sky just beforethe comet passes surprisingly near Mars in space.

VENUS MEETS MOON, SPICA, SATURN. Venus is still not settingmuch later after the Sun. But it’s high enough to beobserved with the three objects it has conjunctions with thismonth. Most spectacular for observers in the Americas isVenus’s very close pairing with a slender crescent Moon onthe evening of September 8. On the previous evening Venuswas only a little more than 1½° from Spica so this nightMoon, planet and Spica form a “trio” (fit within a circle 5° orless in diameter). The next evening—that of September 9—the Moon is not too far left of Saturn. Venus and Saturn pass

each other on the Americas evening of September 19,though the separation is almost 4°. (Mercury is less than 1°from Spica on the American evening of September 24 butthey are quite low in the dusk.)

MARS CROSSES THE BEEHIVE. Magnitude 1.6 Mars is march-ing through the southern part of M44, the Beehive Star clus-ter in Cancer, on the American mornings of September 24and 25. A few nights later Mars has another remarkable tele-scopic encounter (see final Highlight below).

JUPITER RISES IN MIDDLE OF NIGHT. Jupiter rises about 1:45a.m. (daylight saving time) as September begins but just aftermidnight as the month ends. It brightens from about magni-tude —2.0 to —2.2 in a scenic location in Gemini and is grow-ing in telescopes.

SOLAR MAX, THE EQUINOX AND AURORAS. The Sun shouldnow be near the maximum in its roughly 11-year-cycle ofactivity and since the equinoxes are especially favorable forauroras, this month is a prime time to watch for outbreaks ofthe Northern Lights and Southern Lights. One way to keep

posted on the latest sunspots and prominences as well asprospects for auroras is at www.spaceweather.com.

HARVEST MOON AND MOON MEETINGS. This year the mostfamous of Moons, Harvest Moon, happens on September19. The Moon’s meetings other than its ones with Venusand Saturn this month include not very close encounters inthe final hours of night with Mars on September 2 andJupiter on September 28. The Moon is nearing Mars againon September 30.

COMET ISON NEARS MARS IN SPACE, IS PASSED BY MARS IN SKY.On the Americas morning of September 27 Comet ISON is2.0° north of Mars, shining at perhaps about magnitude 10.1.Mars overtakes the comet in our sky in their eastward appar-ent race and forges into the lead—but only for 2½ weeks(see Observers’ Highlights for October). In space, the cometis coming in directly over Mars in its orbit—a pass in spacewhich occurs on October 1 (again, see Observers’ Highlightsfor October).

SWSW225225˚

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Sep. 8, 45 minutes after SUNSETSep. 8, 45 minutes after SUNSET8:05 P.M. EDT (= Sep. 8, 0:05 UT)8:05 P.M. EDT (= Sep. 8, 0:05 UT)

Arcturus

Arcturus

SpicaSpica

SaturnSaturn

VenusVenus

Mercury

Mercury

SunSun 6 6

7 7

Moon

Moon

8 8

9 9

1 0 o

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altitude

Times are given in UT (Universal Time, same as local timeat Greenwich on the 0° meridian of longitude). EDT: clocktimes in eastern U.S.; edt: in previous day.To convert to other times, see world map inside back cover.Positions given for the Moon (such as “2° north of Mars”)are as seen from center of Earth; from north edge of Earth,Moon appears nearly 1° farther south.� � � � Moon new, 1st quarter, full, last quarter² ± ° � amount of Moon-dark time

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3Astronomical Calendar 2013 25

October

± 1 Tue. ( 2 UT=22 edt) Moon 6.4° S.S.W. of Mars (47° from Sun in morning sky).(20 UT=16 EDT) Moon 5.3° S.S.W. of Regulus (about 38° from Sun in morning

sky).± 2 Wed. (12 UT= 8 EDT) 102P Shoemaker 1 at opposition. See COMETS.± 3 Thu. (14 UT=10 EDT) Uranus at opposition. This is the middle of the best time of

year to see it. It is on the meridian at midnight, and now moves from the morning intothe evening sky. For general description and chart see the URANUS section.

(23 UT=19 EDT) Venus at aphelion, 0.7282 a.u. from the Sun.² 5 SAT. ( 0:33 UT=20:33 edt) � Moon new. Beginning of lunation 1123.

(23 UT=19 EDT) Moon 0.93° N.E. of Spica (only about 11° from the Sun)._____________________________________________________weeks____________

² 6 SUN. (22:08 UT=18:08 EDT) Moon at ascending node (longitude 217.8°).(24 UT=20 EDT) Moon 2.8° N.N.E. of Mercury (25° from Sun in evening sky).

± 7 Mon. ( 2 UT=22 edt) Moon 2.0° S.W. of Saturn (about 26° from Sun in evening sky).( 6 UT= 2 EDT) Moon, Mercury, and Saturn within circle of diameter 5.07°;

27° East of the Sun.

± 8 Tue. Draconids or Giacobinids. See METEORS. Very favorable year for this occasionallystrong to storm shower (no activity is predicted).

( 8 UT= 4 EDT) Mercury 5.0° S.S.W. of Saturn (about 25° from Sun in eveningsky); magnitudes 0.0 and 0.6. Conjunction in r.a. is 59 hours later. First part of a tripleconjunction: Mercury retreats past Saturn on Oct. 30, re-overtakes it on Nov. 26.

(14 UT=10 EDT) Moon 4.6° N. of Venus (about 45° from Sun in evening sky).± 9 Wed. ( 3 UT=23 edt) Moon 7.4° N. of Antares (about 53° from Sun in evening sky).

(10 UT= 6 EDT) Mercury at greatest elongation east, 25.3° from the Sun.± 10 Thu. Southern Taurids. See METEORS. Very favorable year for this minor shower.

(23 UT=19 EDT) Moon at perigee. Distance 57.98 earth-radii.± 11 Fri. ( 5 UT= 1 EDT) Moon 2.0° N.W. of Pluto (about 80° from Sun in evening sky).

(23:03 UT=19:03 EDT) � Moon at first quarter.° 12 SAT. Astronomy Day in the fall. See the spring one, Apr. 28.

(15 UT=11 EDT) Jupiter at west quadrature.______________________________________________________________________

° 13 SUN. ( 5 UT= 1 EDT) Moon 1.2° W.S.W. of 3 Juno (about 106° from Sun in eveningsky). See ASTEROIDS.

° 15 Tue. ( 2 UT=22 edt) Moon 5.5° N.N.W. of Neptune (131° from Sun in evening sky).( 7 UT= 3 EDT) Mercury at greatest latitude south of the ecliptic plane (—7.0°).(11 UT= 7 EDT) Mars 0.94° N.N.E. of Regulus (52° from Sun in morning sky);

magnitudes 1.6 and 1.4. Conjunction in r.a. is 13 hours earlier.

° 16 Wed. ( 5 UT= 1 EDT) C/2012 S1 ISON 2.0° N.N.E. of Regulus (53° from Sun inmorning sky). See COMETS.

(22 UT=18 EDT) Venus 1.5° N.N.E. of Antares (46° from Sun in evening sky);magnitudes —4.3 and 1.0. Conjunction in r.a. is 7 hours earlier.

� 17 Thu. (21 UT=17 EDT) Moon 3.3° N. of Uranus (about 165° from Sun in evening sky).� 18 Fri. (17 UT=13 EDT) C/2012 S1 ISON 0.89° N.E. of Mars (about 53° from Sun in

morning sky); magnitudes 8 and 1.5. Conjunction in r.a. was 3 days earlier. See Sep.27.

(23:36 UT=19:36 EDT) � Moon full. See SPECIAL MOONS.Penumbral eclipse of the Moon. See ECLIPSES.

� 19 SAT. (21:47 UT=17:47 EDT) Moon at descending node (longitude 37.7°).______________________________________________________________________

° 21 Mon. Orionids. See METEORS. Very unfavorable year for this major shower.(15 UT=11 EDT) Mercury stationary in right ascension; begins retrograde (west-

ward) motion. The stationary moment in longitude is 5 hours earlier.(17 UT=13 EDT) Moon 6.1° S.S.E. of Pleiades (148° from Sun in morning sky).

° 22 Tue. Creation of the world began at nightfall preceding Sunday Oct. 23 (Julian calen-dar; Sep. 21 Gregorian) in 4004 BC, according to Annals of the Old Testament byArchbishop James Ussher (1650).

(12 UT= 8 EDT) Moon 2.6° N. of Aldebaran (139° from Sun in morning sky).° 23 Wed. ( 6 UT= 2 EDT) Sun enters the astrological sign Scorpio, i.e. its longitude is

210°. But astronomically it is still in Virgo. See Ast. Companion, PRECESSION.° 25 Fri. (14 UT=10 EDT) Moon at apogee. Distance 63.43 earth-radii.

(21 UT=17 EDT) Moon 5.0° S. of Jupiter (102° from Sun in morning sky).(23 UT=19 EDT) Venus at greatest latitude south of the ecliptic plane (—3.4°).

° 26 SAT. ( 2 UT=22 edt) Moon 11.8° S.S.W. of Pollux (about 99° from Sun in morningsky).

(23:41 UT=19:41 EDT) � Moon at last quarter.______________________________________________________________________

± 27 SUN. Last Sunday in Oct.: in Europe, change clocks back to standard time. See lastSunday in March. —In 2005 there was a proposal in Britain not to change clocksback—to keep the artificial “Daylight Displacement Time” all year!

( 6 UT= 2 EDT) Moon 6.6° S.S.W. of Beehive Cluster (about 86° from Sun inmorning sky).

( 9 UT= 5 EDT) 324 Bamberga at perihelion, 1.7812 a.u. from the Sun. SeeASTEROIDS.

± 29 Tue. ( 3 UT=23 edt) Moon 5.4° S.S.W. of Regulus (66° from Sun in morning sky).(21 UT=17 EDT) Moon 6.1° S.S.W. of Mars (58° from Sun in morning sky).

± 30 Wed. (11 UT= 7 EDT) Mercury 3.5° S.S.W. of Saturn (only about 6° from the Sun).Conjunction in r.a. is 39 hours earlier. 2nd part of a triple conjunction; see Oct. 8 andNov. 26.

(20 UT=16 EDT) Theoretical middle of eclipse season: Sun is at same longitudeas Moon’s ascending node, 217.6°. See also May 7.

(24 UT=20 EDT) �� Sun enters Libra, at longitude 217.72° on the ecliptic.± 31 Thu. Hallowe’en (eve of All Saints’ Day, Nov. 1, and All Souls’ Day, Nov. 2), a cross-

quarter day; see Ast. Companion, SEASONS. For a theory on the Hallowe’en pumpkin,see the Harvest Moon of Sep. 19, SPECIAL MOONS.

( 3 UT=23 edt) Venus at theoretical dichotomy, half illuminated as seen fromEarth. But observed time of dichotomy may be several days different.

October is clear and crisp in the eastern U.S., with blue sky and orange trees.

Observers’ highlights for October by Fred SchaafPredictions for Comet ISON’s brightness are from aboutmagnitude 9.8 at the start of October to about 8.5 at mid-month to about 6.5 at month’s end. If Comet ISON is bright-ening to these levels, observing it may be the most excitinghighlight of the month—especially because, by amazing andbeautiful coincidence, it catches Mars in the sky just whenMars catches Regulus!

COMET ISON, MARS, AND REGULUS. On September 27, Marspassed Comet ISON in their eastward race in our sky. Buttheir close encounter in space comes on October 1 whenthe comet passes 0.07 a.u. directly over Mars—hopefullyproviding a target for imaging by the Mars rover Curiosity.Then, at mid-month, Comet ISON catches back up to Marsin our sky, passing just 1.1° north of Mars—while Mars isitself passing less than 1° from slightly brighter Regulus.Sequence of events: Mars 1.0° north of Regulus at 22 UT onOctober 14; Mars 0.9° from Regulus (appulse) at 11 UT onOctober 15; Mars 1.1° south of Comet ISON at 16 UT onOctober 15.

For the second half of October Comet ISON keeps pacewith the Sun remaining almost exactly as many degrees from

the Sun—and achieves a maximum angular separation(“greatest elongation”) of 54° from the Sun on October 23.

ISON CROSSES FROM MARS ORBIT TO EARTH ORBIT. The comettakes exactly a month—from October 1 to November 1—flying from straight above Mars’s orbit to straight aboveEarth’s. Mars is at the point in its orbit when Comet ISONpasses inward; Earth will in mid-January 2014 be at the pointin its orbit that ISON passed above on its way inward—andEarth just might encounter meteors from the comet then.Amazingly, on the comet’s outward pass over Earth’s orbit—on December 26—Earth will be at that point in its orbit.

CLOSE VENUS-ANTARES CONJUNCTION AND VENUS NEARING

GREATEST ELONGATION. Venus passes only 1.5° from Antareson the Americas evening of October 16. Venus will reachgreatest elongation on the Americas night of October 31-November 1, with telescopes showing an exactly half-litVenus close to this time. Venus finally begins to get marked-ly higher at dusk—it follows about 105 minutes after the Sunon October 1 but more than 150 minutes on November 1.

HIGH JUPITER AND LOW MERCURY AND SATURN. BrighteningJupiter rises not long after 10 p.m. by the end of October andis then highest in the south less than 2 hours before sunrise.

Jupiter arrives at west quadrature (90° west of the Sun) onOctober 12. On the Americas morning of October 4 Jupiterpasses just over 6´ north of magnitude 3.5 DeltaGeminorum, also known as Wasat (that’s about a magnitudebrighter than any Galilean satellite ever gets, so try to see thestar with naked eye this close to Jupiter). Mercury is at great-est elongation in the evening sky (and magnitude 0) onOctober 9 but still low as seen from mid-northern latitudes.The day before, Mercury is within 5° of Saturn.

A PENUMBRAL ECLIPSE OF THE MOON is large enough to bevisible where it is best seen, in Europe and Africa on the nightof October 18-19 (see ECLIPSES).

URANUS AT OPPOSITION. Uranus reaches opposition onOctober 3, shining at magnitude 5.7 and appearing 3.7″wide in telescopes (see URANUS)

MOON MEETINGS. The waxing crescent Moon forms anearly equilateral triangle with Venus and Antares on theAmericas evening of October 8. A waning gibbous Moonhinders viewing of the ORIONID meteor shower peak (seeMETEORS). The Moon is well lower right of Jupiter at dawn onOctober 25 and forms a nearly equilateral triangle with Marsand Regulus on October 29.

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Oct. 7, 45 minutes after SUNSETOct. 7, 45 minutes after SUNSET7:18 P.M. EDT (= Oct. 7, 23:18 UT)7:18 P.M. EDT (= Oct. 7, 23:18 UT)

Vega

Antares

Antares

SaturnSaturn

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Mercury

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Times are given in UT (Universal Time, same as local timeat Greenwich on the 0° meridian of longitude). EDT: clocktimes in eastern U.S.; edt: in previous day.To convert to other times, see world map inside back cover.Positions given for the Moon (such as “2° north of Mars”)are as seen from center of Earth; from north edge of Earth,Moon appears nearly 1° farther south.� � � � Moon new, 1st quarter, full, last quarter² ± ° � amount of Moon-dark time

° 25 Mon. ( 1 UT=20 est) C/2012 S1 ISON 1.2° S. of 2P Encke (15° from Sun in morningsky).

(13 UT= 8 EST) Moon 5.3° S.S.W. of Regulus (93° from Sun in morning sky).(19:29 UT=14:29 EST) � Moon at last quarter.(23 UT=18 EST) Mars at greatest latitude north of the ecliptic plane (1.8°).

± 26 Tue. ( 1 UT=20 est) Mercury 0.31° S.S.W. of Saturn (about 17° from Sun in morn-ing sky); magnitudes —0.7 and 0.6. Conjunction in r.a. is 3 hours later. 3rd and clos-est part of a triple conjunction; see Oct. 8 and 30.

± 27 Wed. (13 UT= 8 EST) Moon 5.4° S.S.W. of Mars (about 70° from Sun in morning sky).± 28 Thu. (23 UT=18 EST) C/2012 S1 ISON at perihelion. See COMETS.± 29 Fri. (19 UT=14 EST) Moon 1.3° E.N.E. of Spica (about 43° from Sun in morning sky).

Occultation.

± 30 SAT. ( 0 UT=19 est) �� Sun enters Ophiuchus, at longitude 247.95° on the ecliptic.This is not one of the twelve traditional houses of the Sun; see Ast. Companion, ZODI-AC.

(17:01 UT=12:01 EST) Moon at ascending node (longitude 217.5°).

In November evenings the Milky Way spans the sky symmetrically from east to west (pass-ing straight overhead for those who live about latitude 60° north).

We therefore now have our most open view out of the “south window” of our galaxy—as in May we had a much more open view out of its “north window.” Out of this south win-dow we look into the middle of our Local Group of galaxies, seeing our neighbors inAndromeda, Triangulum, Dorado, etc.; whereas out of the north window we looked inwardon the vaster supercluster (centering in Virgo) on whose edge our group hovers. See Ast.Companion, OUTRUSH.

Overflow of November, caused by the comet

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AQUAR I US

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Mar


SPATIAL VIEW of the orbits of the inner planets during thefirst quarter of the year. This picture is heliocentric: theSun is the fixed point and origin for measurements. Theviewpoint in this and other spatial views in the book isfrom ecliptic longitude 230°, latitude +35°, in the head ofthe constellation Serpens, so that the 23½° tilt of the eclip-tic plane to the equatorial plane can be seen. This view isfrom a distance of 6 astronomical units (a.u.) from theSun. On an imaginary sphere, 2 a.u. out, are shown theplanes of the equator and ecliptic, and the boundaries of

the zodiacal constellations. The planets move nearly in theecliptic plane, so as seen from the Earth they appearagainst the background of these constellations (except thatpart of the ecliptic, in the foreground, lies in Ophiuchusrather than Scorpius). Along the orbital paths, globes rep-resent the planets at the start of each month. Their size isexaggerated 500 times, the Sun’s only 5 times. When aplanet is in or north of the ecliptic plane, its path is drawnwith a thicker line. When it is in the morning sky (west ofthe Sun) as seen from the Earth, its course is shown in gray.

MERCURY’S APPARITIONS compared. Blue areas represent morning apparitions(westward elongation); gray, evening apparitions (eastward). The top figures are themaximum elongations (angular distances Mercury attains from the Sun), reached at thetop dates shown beneath. Curves show the altitude of Mercury above the horizon atsunrise or sunset, for latitude 40° north (thick line) and 35° south (thin), with maximareached at the parenthesized dates below (40° north bold). For example in MarchMercury reaches a maximum westward elongation of 27.8°, and a maximum altitudeof 26.7° above the sunrise horizon for latitude 35° south, but only 10.3° for 40° north.

ARIESARIES

CANCER

CANCERGEMINIGEMINI

LEOLEO

PISCES

PISCES

TAURUSTAURUS

Procyon Mira

CastorCastor

PolluxPollux

Regulus

Regulus

Betelgeuse

AldebaranAldebaran

AprAprMayMayJunJun

JulJul

AugAug

MayMay

JunJun

JulJul

AugAug

SepSep

May

24

May

24

Jun

20Ju

n 20

-10-10˚

0˚

+10+10˚180180˚ 165165˚ 150150˚ 135135˚ 120120˚ 105105˚ 9090˚ 7575˚ 6060˚ 4545˚ 3030˚ 1515˚ 0˚

+10+10˚

0˚

-10-10˚ 1h

2h

3h

4h

5 h 6 h 7 h 8 h

9 h 1 0 h

1 1 h

1 2 h

+ 3 0 o+2 0 o

+1 0 o

e q u at o

r

eq

ua

t or

e c l i p t i ce c l i p t i c

Mi

lk

y

Wa

y

El NathEl Nath PleiadesPleiades

Venus

Mercury

CONTINUATIONS of the motions of Mercury,Venus, and Earth in the other quarters of the year.The Earth goes around the Sun once in the year,but Venus 1.625 times and Mercury 4.15 times.

--4--3--2--101

m a g n i t u d e s

lain so far south since 1938. Here are its southernmost declinationsof —27° or more in the 20th and 21st centuries:

Notice that these dates, at the characteristic 8-year intervals, formtwo series. The first was its deepest further back, on 1874 Nov. 6:—28°05´ (according to Jean Meeus, Astronomical Tables, p.36). Thenthe maxima become less extreme. Then, after the 1938-1997 gap ofslighter maxima, another series took over.

Interesting in its own numerical sort of way, like many of the pat-terns thrown up by astronomy, but what is interesting for us asobservers is that only the three least extreme of these southernmost-declinations coincide closely enough with dates of easternmost elon-gation that these also take place south of —27°. In 1997 easternmostelongation was just 0.65 day earlier; in 2005, 3.00 days earlier; in2013, 5.38 days earlier. That’s why this type of year has (for ournorthern hemisphere) low evening displays of Venus.

In the tail of the year Venus starts groping back north on thecelestial map, but begins its slide down in the sunset sky, toward itsnext passage in front of (and 5° north of) the Sun on 2014 Jan. 11.horizon

18.2˚

Mar 5

17.0˚

(Mar 5)

7.6˚

(Feb 29)

27.5˚

Apr 18

9.7˚

(Apr 15)

26.2˚

(Apr 18)

25.7˚

Jul 1

16.8˚

(Jun 24)

20.8˚

(Jul 5)

18.7˚

Aug 16

16.1˚

(Aug 18)

11.1˚

(Aug 12)

24.1˚

Oct 26

8.1˚

(Oct 28)

22.9˚

(Oct 26)

20.5 20.5˚

Dec 4 Dec 4

17.0 17.0˚

(Dec 3)(Dec 3)

11.9 11.9˚

(Dec 10)(Dec 10)

20122012

horizonhorizon

18.1 18.1˚

Feb 16 Feb 16

16.5 16.5˚

(Feb 17)(Feb 17)

8.7 8.7˚

(Feb 12)(Feb 12)

27.8 27.8˚

Mar 31 Mar 31

10.3 10.3˚

(Mar 24)(Mar 24)

26.7 26.7˚

(Apr 1)(Apr 1)

24.3 24.3˚

Jun 12 Jun 12

18.4 18.4˚

(Jun 8)(Jun 8)

16.9 16.9˚

(Jun 17)(Jun 17)

19.6 19.6˚

Jul 30 Jul 30

15.6 15.6˚

(Aug 2)(Aug 2)

13.2 13.2˚

(Jul 26)(Jul 26)

25.3 25.3˚

Oct 9 Oct 9

7.9 7.9˚

(Oct 4)(Oct 4)

24.4 24.4˚

(Oct 9)(Oct 9)

19.5 19.5˚

Nov 18 Nov 18

17.2 17.2˚

(Nov 17)(Nov 17)

9.4 9.4˚

(Nov 21)(Nov 21)

Mercury 2013Mercury 2013

horizon

18.4 18.4˚

Jan 31 Jan 31

15.9 15.9˚

(Feb 1)(Feb 1)

10.3 10.3˚

(Jan 27)(Jan 27)

27.5˚

Mar 14

11.3˚

(Mar 5)

26.3˚

(Mar 15)

22.7˚

May 25

19.2˚

(May 22)

12.9˚

(May 30)

20.9˚

Jul 12

14.7˚

(Jul 17)

15.8˚

(Jul 9)

26.4˚

Sep 21

8.7˚

(Sep 11)

25.4˚

(Sep 21)

18.7˚

Nov 1

17.1˚

(Nov 1)

7.8˚

(Nov 2)

20142014

1906 Nov 3 -28°00’

1914 Nov 1 -27 51

1922 Oct 31 -27 40

1930 Oct 29 -27 26

1938 Oct 28 -27 09

1997 Nov 6 -27 00

2005 Nov 6 -27 04

2013 Nov 6 -27 09

2021 Nov 6 -27 14

2029 Nov 6 -27 18

2037 Nov 6 -27 23

2045 Nov 6 -27 29

2053 Nov 6 -27 34

2061 Nov 6 -27 39

2069 Nov 6 -27 44

2077 Nov 6 -27 49

2085 Nov 6 -27 53

2093 Nov 6 -27 57

(continued)

MERVEN.qxd 22/10/2012 02:15 Page 49

Astronomical Calendar 2013 73Maps for selected occultations, showing areas of the Earth within which they are visible during darkness. Arrows point intothe areas of visibilty; dashed lines are the limits beyond which visibility would be in twilight. Maps drawn by Richard Nugent.

Jan 5 Spica

On the evening of September 7, the asteroid 1465 Autonoma willoccult the mag. 3.6 star Algedi (6 Cap) for up to 3.4 seconds acrossthe Hawaiian Islands. The asteroid’s 19-km-wide shadow pathcrosses the islands just a few seconds before 7:01 UT (9:01 PMHawaiian time). The solid lines indicate the predicted path, dashedlines indicate the limits of uncertainty in the path. Although thepath prediction has a large error, updates to the path wil be post-ed on IOTA’s asteroid occultation website (see text) one monthbefore the event. This event is definitely worth a look!

Autonoma was discovered on March 20, 1938, by Arno ArthurWachmann at Bergedorf in Germany. Wachmann discovered 3asteroids and 3 comets.

Feb 18 Jupiter

Feb 2 SpicaJan 23 Zeta TauriJan 22 Jupiter

Mar 30 Alpha LibraeMar 28 SpicaMar 1 Spica

Aug 14 Alpha LibraeJun 18 SpicaApr 25 SpicaMar 31 Acrab

Nov 29 SpicaOct 5 Spica

Sep 8 SpicaSep 8 Autonoma occults Algedi

Dec 27 Spica Dec 28 Alpha Librae

2013 Sep. 8 15h2013 Sep. 8 15hSpicaSpicamag. 1.0mag. 1.0elong. 37elong. 37˚ E E

2013 Oct. 5 22h2013 Oct. 5 22hSpicaSpicamag. 1.0mag. 1.0elong. 11elong. 11˚ E E

2013 Nov. 2 7h2013 Nov. 2 7hSpicaSpicamag. 1.0mag. 1.0elong. 16elong. 16˚ W W

2013 Sep. 8 21h2013 Sep. 8 21hVenusVenusmag. -4.1mag. -4.1elong. 40elong. 40˚ E E

Views toward Earth from the direction of a star or planet as the Moonpasses between; its “shadow” is drawn at mid occultation (given inUT to the nearest hour) and an hour before and after. These shad-ows define the track on Earth within which the occultation isvisible—but not exactly, because the turning of the Earth is not takeninto account. (An arrow on the equator shows how much Earthrotates in two hours.) “Mag.” is the magnitude of the occulted body;“elong.,” its angular distance from the Sun.

Side-diagrams (with celestial north attop) show the phase of the Moon, with theocculted body passing behind it at intervalsof 10 minutes over the same 2 hours, as seenfrom the center of Earth. From places northof Earth’s center, the Moon will appear far-ther south.

Spica is occulted at every passage of theMoon this year; each time, the occultationpath passes slightly farther north, theMoon’s phase gradually changes, and theEarth is caught at a different moment of itsrotation.

On Sep. 8, the Moon occults not only thefixed target of Spica but the moving target ofVenus.

OCC13.qxd 22/10/2012 02:34 Page 73


MarsMars

MarsMars

Alde

baran

Alde

baran

-27-27

-26-26

-13-13

-12-12

-11-11

-10-10

-9 -9

-8 -8

-7 -7

-6 -6

-5 -5

-4 -4

-3 -3

-2 -2

-1 -1

0 0

+1 +1

+2 +2

+3 +3

+4 +4

+5 +5

+6 +6

+7 +7

+8 +8

+9 +9

+10+10

+11+11

+12+12

+13+13

+14+14

+15+15

+16+16

+17+17

+18+18

+19+19

+20+20

+23+23

+24+24

+25+25

+26+26

JanJan FebFeb MarMar AprApr MayMay JunJun JulJul AugAug SepSep OctOct NovNov DecDec

----fi

reb

alls-

-----------------

----fi

reb

alls-

-----------------

-1.4 Sirius-1.4 Sirius

-0.7 Canopus-0.7 Canopus ---naked-eye in daytime sky? ---naked-eye in daytime sky? 0.0 Arcturus, Vega, Capella 0.0 Arcturus, Vega, Capella

1.4 Regulus 1.4 Regulus

2.1 Polaris 2.1 Polaris

3.5 naked-eye limit, in cities 3.5 naked-eye limit, in cities

5 ----average conditions 5 ----average conditions

6.5 ----good conditions 6.5 ----good conditions

8.6 ----through blackened tube 8.6 ----through blackened tube 9 2-inch binoc., 1-inch tel. 9 2-inch binoc., 1-inch tel.

10.5 2-inch (5-cm) telescope10.5 2-inch (5-cm) telescope11 Proxima Centauri11 Proxima Centauri11.4 3-inch (8-cm) telescope11.4 3-inch (8-cm) telescope

12.9 6-inch (15-cm)12.9 6-inch (15-cm)13.5 8-inch (20-cm)13.5 8-inch (20-cm)

14.4 12-inch (30-cm)14.4 12-inch (30-cm)

19.5 200-inch (508-cm), visual19.5 200-inch (508-cm), visual

23.5 ----photographic23.5 ----photographic

(28) faintest objects(28) faintest objects photographed photographed(31) faintest objects recorded(31) faintest objects recorded with Hubble Space Tel. with Hubble Space Tel.

Mo

on

Mo

on

oppoppPlutoPluto

conjconj

oppoppNeptuneNeptune

conjconj

oppoppUranusUranus

oppoppconjconjSaturnSaturn Saturn without ringsSaturn without rings

conjconj

JupiterJupiter

conjconjMarsMars

sup conjsup conj

inf conjinf conj

sup conjsup conj

inf conjinf conj

sup conjsup conj

inf conjinf conj

sup conjsup conj

Mercury

Mercury

Mercury

Mercury

sup conjsup conjVenusVenus

1 Ceres1 Ceres

1 Ceres1 Ceres

2 Pallas2 Pallas

3 Juno3 Juno

3 Juno3 Juno

4 Vesta4 Vesta

4 Vesta4 Vesta

324 Bamberga324 Bamberga

324 Bamberga

324 Bamberga

C/2012 K5 LINEAR

C/2012 K5 LINEAR

C/2

011

L4

C/2

011

L4PA

NST

ARR

S

PAN

STA

RRS

C/2012 F6 Lemmon

C/2012 F6 Lemmon

63P Wild 163P Wild 1

102P Shoemaker 1

102P Shoemaker 1

2P Encke2P Encke

154P Brewington

154P Brewington

P/1998 U3 Jaeger

P/1998 U3 Jaeger

29P Schwassmann-Wachmann 129P Schwassmann-Wachmann 1

SunSun

eclipseeclipseeclipseeclipse

eclipseeclipse eclipseeclipseeclipseeclipse

asteroid

s

asteroid

s

comets

comets

1 8 0 o

1 7 0 o

1 6 0 o

1 5 0 o

1 4 0 o

1 3 0 o

1 2 0 o

1 1 0 o

1 0 0 o

9 0 o

8 0 o

7 0 o

6 0 o

5 0 o

4 0 o

3 0 o

2 0 o

1 0 o

0 o

1 0 o

2 0 o

3 0 o

4 0 o

5 0 o

6 0 o

7 0 o

8 0 o

9 0 o

1 0 0 o

1 1 0 o

1 2 0 o

1 3 0 o

1 4 0 o

1 5 0 o

1 6 0 o

1 7 0 o

1 8 0 o

JanJan FebFeb MarMar AprApr MayMay JunJun JulJul AugAug SepSep OctOct NovNov DecDec

weste

rn (

mo

rnin

g s

ky)

weste

rn (

mo

rnin

g s

ky)

easte

rn (

evenin

g s

ky)

easte

rn (

evenin

g s

ky)

Antares

Antares

Antares

Antares

Spica

Spica

Spica

Spica

Regu

lus

Regu

lus

Regu

lus

Regu

lus

Beeh

ive

Beeh

ive

Beeh

ive

Beeh

ive

Pollu

x

Pollu

x

Pollu

x

Pollu

x

Alde

baran

Alde

baran

Alde

baran

Alde

baran

Pleia

des

Pleia

des

Pleia

des

Pleia

des

Pluto

Pluto

Pluto

Pluto

Pluto

Pluto

Nep

tune

Nep

tune

Nep

tune

Nep

tune

Nep

tune

Nep

tune

Uranu

s

Uranu

s

Uranu

s

Uranu

s

Uranu

s

Uranu

s

Saturn

Saturn

Saturn

Saturn

Jupiter

Jupiter

Jupiter

Jupiter

Mercury

Mercury

Mercury

Mercury

VenusVenus

VenusVenus

SunSun

Mo

on

Mo

on

eclipseeclipse

eclipseeclipse

eclipseeclipse

eclipseeclipse

eclipseeclipse

102P Shoemaker 1

102P Shoemaker 1

MercuryMercury

Mo

on

Mo

on

Satu

rn

Satu

rn

Regu

lus

Regu

lus

Beeh

ive

Beeh

ivePo

llux

Pollu

x

Pleia

des

Pleia

des

Mo

on

Mo

on

C/2012 S1C/2012 S1ISONISON

2P2PEnckeEncke

ISON

ISON

ISO

NIS

ON

Come

Come

C/20

12 S1

C/20

12 S1

ISON

ISON

C/2

012

S1C

/201

2 S1

ISO

NIS

ON

is the time when Earth is closer to them. A dotted curve showsthe brightness of the ball of Saturn alone, without its brilliantrings (which, opening out since they were edge-on to us in2009, contribute in April and May nearly 0.7 of a magnitude).

The Moon at first and third quarter is not, as one might sup-pose, half as bright as full (which would put it only 0.75 of amagnitude lower on the graph) but only about 1/11 as bright(2.6 magnitudes lower). See Ast. Companion, MOONLIGHT.

Asteroid names are preceded by simple numbers, as in “1Ceres.” “P” distinguishes periodic comets, “C” long-periodones. Comets may behave unpredictably in brightness and fol-low quite different curves from those shown.

Magnitudes given are visual. Photographic magnitudes areabout 0.7 to 0.9 greater (fainter); the peak sensitivity for tradi-tional astronomical film is slightly blue-ward from that for thehuman eye. Magnitudes are calculated taking into accountphase-angle (the angle Sun-body-Earth; hence, the part of thebody that is in shadow).

ELONGATIONTry rotating the page so that January is at the top and the plan-ets moving downward. There are two ways to look at it:

—Planets revolving around a star, as seen from one of thoseplanets. The motion of Mercury and Venus resembles thecorkscrew motion of the satellites around Jupiter. But the otherplanets slip always backward (Mars least fast), because, beingfarther out than us, they are losing the race with us around theSun. The Moon, searing repeatedly across the foreground,describes a kind of time-cylinder around us.

—Imagine the diagram cut in half along the Sun-line, andput back the other way around: 0° (the Sun-line) at left and right,and 180° down the center. The Sun-line now represents thedawn horizon (on the left) and the sunset horizon (on the right).The line down the new middle (180°) is the meridian at mid-night; the graph has become a graph of the night sky’s wholeexpanse, from sunset to sunrise. On the new right, the superi-or planets (including, this year, Mars) sink into the sunset hori-

zon; Mercury bobs up into view from it three times; Venus heaves slowly up from it; theyoung Moon leaps repeatedly out of it. In the new middle, the superior planets (except,this year, Mars and Jupiter) are shown crossing the midnight meridian at their oppositions,when they are brightest. On the new left, the dawn horizon, the superior planets (includ-ing Mars) emerge from their conjunctions with the Sun; Mercury keeps bobbing out onthis side also; Venus early sinks into it; and the waning Moon dives repeatedly.

The crossing of any two lines represents a conjunction. A planet is at conjunction withthe Sun if it crosses the 0° line, and at opposition if it crosses the 180° line. At 90° eastor west of the Sun, a planet is said to be at east or west “quadrature.”

The Moon is New when it crosses 0°; Full at 180°; at First and Last Quarter when it is90° east or west. It is at conjunction with planets when it crosses their lines. The diagramreveals the times when the Moon fills the midnight, morning or evening sky with glare,and times when its narrow crescent (near to the Sun) joins groupings of planets.

The greatest elongation Venus reaches can vary between about 45.4° and 47.3°. Thisyear it reaches 47.1° east. The greatest for Mercury varies between 17.87° and 27.83°;this year it reaches 18.1°, —27.8°, 24.3°, —19.6°, 25.3°, —19.5° (negative meaning west-ward). The asymmetry of its swings is caused by its elliptical orbit: if at one elongation itis at perihelion, at the next it will be near (not at) aphelion. For north-hemisphereobservers it is not usually highest above the horizon when at the larger maxima of elon-gations; see the MERCURY section.

Elongation really means angular distance measured from the Sun in any direction, notjust along the ecliptic (difference in longitude). Even at conjunction, a planet is usually alittle north or south of the Sun; at opposition it is north or south of the anti-Sun point.Therefore elongation usually doesn’t exactly reach 0° or 180°; instead, the lines on thegraph curl away a little before reaching these limits, then after a jump resume on the otherside. This is noticeable for Mercury at inferior conjunctions where it passes well north orsouth of the Sun. It is no longer as noticeable as it used to be for Pluto, which now liesonly about 3° north of the ecliptic.

Stars too can be said to have elongation from the moving Sun. Shown are the fivebright stars and two clusters (Pleiades and Beehive or Praesepe) near the ecliptic, oftenseen in conjunctions with the Moon and planets. They serve to relate the rest of this time-diagram to the spatial background of the sky. Notice that Pollux, lying more than 7° northof the ecliptic, cannot have elongation less than that. Lines for stars further from the eclip-tic would curl away even more; a star at the ecliptic pole always has elongation 90°.

The graph strictly shows the bodies’ angular relations to the Sun, not to each other.Yet it serves to reveal times when they move side by side or in contrary directions, leavelarge parts of the sky bare, or gather in knots (visited fleetingly by the Moon).

The outer planets are now spread rather evenly around the sky. The nearest to a group-ing is Uranus-Neptune-Pluto, still in their outward order and becoming slowly morespread. Ahead of them is Jupiter (now in the northernmost arch of the ecliptic) andbehind them Saturn; these two were opposite to each other in 2011 and Jupiter advancesrelentlessly to catch up with Saturn in 2020. All planet-planet conjunctions are caused byMars, Venus and especially Mercury eddying around in the foreground.

The sharp points in Comet ISON’s curves (in both graphs) are at its perihelion.

MAGNITUDE—is the astronomical way of measuring brightness. Each magnitude is roughly 2.5times brighter than the one below it. (Magnitude 5 is exactly 100 times brighterthan magnitude 10.) This graph shows the apparent magnitude (that is, as seenfrom the Earth) of solar-system bodies.

The graphs of magnitude and elongation together show the best times of yearto see each moving body. It is more easily seen (1) the brighter it is and (2) thefarther it is from the direction of the Sun. In the magnitude graph, gray lines areused when a body’s elongation from the Sun is less than 15°.

Ticks on the Mercury and Venus curves mark superior conjunctions with theSun (upward ticks) and inferior conjunctions (downward). For other bodies theymark opposition (upward) and conjunction with the Sun (downward).

Superior planets (Mars outward) are brightest near opposition, but all planetsbrighten slightly (in Mercury’s case, a lot) at superior conjunction, because pre-senting their full faces toward us. This is in theory only, as we usually cannot seethem past the Sun. Generally, planets other than Venus are on an upward slopeof brightness when seen in the morning sky, a downward slope in the evening sky.

The curves are drawn thicker when the bodies are retrograding: in general this

MGEG.QXD 22/10/2012 02:42 Page 80

RISING AND SETTINGThis hourglass shows times when the Sun, Moon, andplanets rise and set, for latitude 40° north, longitude 0°.(They differ little for other longitudes, much more forother latitudes.) These are local mean times; to adjustthem to your clock time, see the “Personal Reminder”on the preceding page.

The lines representing days (actually drawn only fordays 1, 6, 11, 16, 21, 26 of each month) begin at mid-night, which is in the middle because we choose toshow night rather than day undivided. Each day-lineends at the point where the next day starts, so there is

really just one time-line, a cut and flattened helix.The dark zone down the middle is night, between

the curves of sunset and sunrise. The three borderinggray bands are the times of civil, nautical, and astro-nomical twilight, when the Sun is less than 6°, 12°, and18° below the horizon.

Slanting lines show the hours of sidereal time: thatis, which hour of right ascension is on the meridian.Thus 0h-1h sidereal time is the “Andromeda Hour,”when that gore of the sky is highest. Sidereal hours are10 seconds shorter than clock (solar) hours and thus fall4 minutes earlier each day.

The times of the Sun’s transit across the meridian

are shown by orange spots. This time differs frommean noon by the amount called the “equation oftime.” At a planet’s opposition it is up all night(roughly) and none of the day.

Meteor showers are marked at the local timeswhen their radiants are highest.

Two thick vertical lines, displaced to the left insummer, represent 5 p.m. and 8 a.m. by the clock (forplaces on the meridian of their time zone). Thisshows how the purpose of setting clocks back fromstandard to “daylight-saving” time is to approximate tothe earlier rising of the Sun. In summer we call thetrue 7 o’clock “8,” the true 12 “1,” etc.

local mean timelocal mean time

2013

0

0

1

1

2

2

3

3

4

4

5

5

6

6

7

7

8

8

9

9

1010

1010

1111

1111

1212 1212

1212 1212

1313

1313

1414

1414

1515

1515

1616

1616

1717

1717

1818

1818

1919

1919

2020

2020

2121

2121

2222

2222

2323

2323

1 1 1 1

1111 1111

Janu

ary

Janu

ary

2121 2121

1 1 1 1

1111 1111

Febr

uary

Febr

uary

2121 2121

1 1 1 1

1111 1111

Mar

chM

arch

2121 2121

1 1 1 1

1111 1111

Apr

ilA

pril

2121 2121

1 1 1 1

1111 1111

May

May

2121 2121

1 1 1 1

1111 1111

June

June

2121 2121

1 1 1 1

1111 1111

July

July

2121 2121

1 1 1 1

1111 1111

Aug

ust

Aug

ust

2121 2121

1 1 1 1

1111 1111

Sept

embe

rSe

ptem

ber

2121 2121

1 1 1 1

1111 1111

Oct

ober

Oct

ober

2121 2121

1 1 1 1

1111 1111

Nov

embe

rN

ovem

ber

2121 2121

1 1 1 1

1111 1111

Dec

embe

rD

ecem

ber

2121 2121

1 1 1 1

0 0

0 0

hours of sidereal tim

e


e

PISCES

PISCES

PISCES

PISCES 2 2

2 2ARIES

ARIES

ARIES

ARIES 4 4

4 4TAURUS

TAURUS

TAURUS

TAURUS 6 6

6 6


e


e

GEM

INI

GEM

INI

GEM

INI

GEM

INI 8 8

8 8CANCER

CANCER

CANCER

CANCER1

010

10

10LE

OLE

O

LEO

LEO1

212

12

12


e


e

VIRGO

VIRGO

VIRGO

VIRGO1

414

14

14LI

BRA

LIBRA

LIBRA

LIBRA1

616

16

16S

CORPIU

S

SCORPIU

S

SCORPIU

S

SCORPIU

S18

18

18

18


e


e

20

20

20

20C

APRIC

ORNUS

CAPRIC

ORNUS

CAPRIC

ORNUS

CAPRIC

ORNUS2

222

22

22

AQUARIU

S

AQUARIU

S

AQUARIU

S

AQUARIU

S

5 p.

m. c

lock

tim

e5

p.m

. clo

ck ti

me

5 p.

m. c

lock

tim

e (s

umm

er)

5 p.

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e (s

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5 p.

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tim

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8 a.

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me

Sun

tran

sits

Sun

tran

sits

Sun

tran

sits

Sun

tran

sits

Sun

tran

sits

Sun

tran

sits

Sun

tran

sits

Sun

tran

sits

Plut

o ris

es

Plut

o ris

es

Pluto ris

es

Pluto ris

es

Pluto ris

es

Pluto ris

es

Pluto se

ts

Pluto se

ts

Pluto se

ts

Pluto se

ts

Pluto se

ts

Pluto se

ts

Nep

tune

rise

s

Nep

tune

rise

s

Nep

tune

rise

s

Nep

tune

rise

s

Nep

tune

rise

s

Nep

tune

rise

s

Nep

tune

sets

Nep

tune

sets

Nep

tune

Nep

tune

sets

sets

Nep

tune

sets

Nep

tune

sets

Uranu

s rise

s

Uranu

s rise

s

Uranu

s rise

s

Uranu

s rise

s

Uranu

s rise

s

Uranu

s rise

s

Uranu

s sets

Uranu

s sets

Uranu

s sets

Uranu

s sets

Uranu

s sets

Uranu

s sets

Satu

rn ri

ses

Satu

rn ri

ses

Saturn

rises

Saturn

rises

Saturn rises

Saturn rises

Saturn se

ts

Saturn se

ts

Saturn

Saturn

sets

sets

Saturn se

ts

Saturn se

ts

Jupi

ter r

ises

Jupi

ter r

ises

Jupiter r

ises

Jupiter r

ises

Jupiter r

ises

Jupiter r

ises

Jupi

ter s

ets

Jupi

ter s

ets

Jupiter s

ets

Jupiter s

ets

Jupiter s

ets

Jupiter s

ets

Mar

s ri

ses

Mar

s ri

ses

Mar

s ri

ses

Mar

s ri

ses

Mar

s ri

ses

Mar

s ri

ses

Mar

s se

tsM

ars

sets

Mars sets

Mars sets

Mar

s se

ts

Mar

s se

ts

Venus rises

Venus rises

Venus risesVenus rises

Venu

s rise

s

Venu

s rise

s

Ven

us s

ets

Ven

us s

ets

Venus sets

Venus sets

Venu

s set

s

Venu

s set

s

Mer

cury

rise

s

Mer

cury

rise

s

Mercury rises

Mercury rises

Mercury rises

Mercury rises

Mercury sets

Mercury sets

Mercury sets

Mercury sets

Pluto oppositionPluto opposition

Neptune oppositionNeptune opposition

Uranus oppositionUranus opposition

Saturn oppositionSaturn opposition

QuadrantidsQuadrantids

LyridsLyrids

EtaEtaAquaridsAquarids

JuneJuneBootidsBootids

DeltaDeltaAquaridsAquaridsAlphaAlpha

CapricornidsCapricornidsPerseidsPerseids

Alpha AurigidsAlpha Aurigids

SeptemberSeptemberEpsilonEpsilon

PerseidsPerseids

DraconidsDraconidsSouthern TauridsSouthern Taurids

OrionidsOrionids

Northern TauridsNorthern Taurids

LeonidsLeonids

AlphaAlphaMonocerotidsMonocerotids

GeminidsGeminids

UrsidsUrsids

first-quarter Moon sets

last-quarter Moon rises

full Moon culminatesfull Moon rises

new Moon setsfirst-quarter Moon culminates

new Moon rises

full Moon setslast-quarter Moon culminates

Merc

ury se

ts

Merc

ury se

ts

sunset at equatorsunset at equator

sunset 20 Nsunset 20 N

sunset 60 N

sunset 60 Nsunset 40 Nsunset 40 N

sunset at equatorsunset at equator

sunset 20 Nsunset 20 Nsunset 60 N

sunset 60 N

sunset 40 Nsunset 40 N

USAUSA

EuropeEurope

USAUSA

EuropeEurope

USAUSA

EuropeEurope

USAUSA

EuropeEurope

2013

Com

et IS

ON

ris

es

Com

et IS

ON

ris

es

Comet

ISON ri

ses

Comet

ISON ri

ses

Comet ISON rises

Comet ISON rises

Comet IS

ON se

ts

Comet IS

ON se

ts

Comet

ISON se

ts

Comet

ISON se

ts

Comet ISON sets

Comet ISON sets

Comet ISON rises

Comet ISON rises

RISING AND SETTING


RISSET.qxd 22/10/2012 02:44 Page 82

2013_AC_Sample01

Documents

2012 s1 ison

double star

september

greatest latitude

greatest latitude

eastern standard

beehive star

suns north