Astronomical coordinates and planning observations Ijorge/aga5802_2017/2017_05_coordenadas1.… · AGA5802 Astrofísica Observacional Astronomical coordinates and planning observations

AGA5802 Astrofísica Observacional

Astronomical coordinates and planning observations I

Bibliography: Any book (or chapter) on coordinates.

Some basic astrometry in slides from Prof. Roberto Boczko + myself (Elementos de Astronomia):

http://www.astro.iag.usp.br/~jorge/aga205_2011/

Prof. Jorge Meléndez 1

Iguazu falls http://www.twanight.org

http://apod.nasa.gov/apod/ap100514.html

Finding the South

-50 -55 -60 -65 -70 -75 -80 -85 -90

14h

15h

16h

Finding the South

-50 -55 -60 -65 -70 -75 -80 -85 -90

14h

15h

16h

Local coordinates

Linha do

Horizonte

Zenith

Nadir

Vert

ical

Slide adapted from Prof. Boczko

Local Meridian

Zenith

N S

E

W

Nadir

Horizon

Is the semicircle

passing through

the points

zenith, N and S.


Altazimutal System Azimuth (A): N E S O(W)

Fig. 3.2 from Astronomy Methods

Altitude (h):

-90o a +90o

Altitude & zenith distance

Horizon

Zenith

Nadir

S

W

E h = altitude z = zenith distance

z

N h

Altitude is the angle between the local horizon and the object

Zenith distance is the angle between the object and the zenith

h + z = 90o


l

j < 0

j

NP

SP

Greenwich

North

East

(S) -900 j +900 (N)

0 l +1800 (E, W) (W) -1800 l +1800 (E)

Longitude l

Geographic system

Latitude j


Sampa? 23.55° S 46.63° W

How to find the Latitude

j

hPole


The altitude of the pole is the latitude of the observer

http://www.wlcastleman.com/astro/qaf05/astrophotos/startrail_1200.htm

La Silla/ESO (3,6m telescope) 29.2612° S, 70.7313° W on 2014/01/12 © J. Meléndez

j

Equatorial

system NP

SP

g a

d

(a , d ) p

a = right ascension

d = declination

p = polar distance

p + d = 900 N

E


Zero point

for R.A. :

intersection

of ecliptic &

equator

Polo

Celeste

Norte

Sun

Equatorial

system

g Vernal equinox

Obliquity of the ecliptic

23o 27' 08"

Equatorial

coordinates

Fig. 3.1 from Astronomy Methods

Units

1 hour 150

0h a < 24h

00 a < 3600

Right Ascension Declination

(S) -900 d +900 (N)

(N) 00 p +1800 (S)

Polar distance


Example: equatorial coordinates for

the Sun

g

W

1

2

NP

PNE

a = 6h

d = +

a = 18h

d = -

4 a = 0h

d = 00

a = 12h

d = 00

3

a = 6h a = 18h

SP Slide adapted from Prof. Boczko

Zero point is the Vernal equinox, about March 21

Horizontal & Equatorial system for

observer in the NH Z

NP

E

W

N S


Provinha 2 4. Plot both horizontal + equatorial system for an

observer in São Paulo. Show the horizontal and

equatorial planes, the zenith, the cardinal points and the

position of the Celestial South Pole

Local Meridian and Projection Z

SP

N S

E

W

Nadir

Horizon

Zenith

Nadir

Horizonte E W

SP

S N

Projection on the meridian plane


Hour circle: the great circle passing

through the object and the celestial poles NP

SP

Z

H d

( H , d )

H = hour angle

d = declination

p = polar distance

W

N S

E

p NP

SP

Observer in the

Northern H.


Hour angle H: the angle measured (on the

equator’s plane) from the local meridian to the object’s

hour circle

Units

(E) -1800 H +1800 (W)

1 hour 150

(E) -12h H +12h (W)

(S) -900 d +900 (N)

00 p +1800

Hour angle Declination

1 h = 15° 1 m = 15' 1 s = 15"

Provinha oral

3h 20m = 0 ‘ “? -300,5 = h m s ?

Culmination or Meridian crossing

NP

Horizon

W

S

At lower meridian crossing: H = 180o

L

SP

Z At upper meridian crossing H = 0.

M

N


Horizon

S

12

At lower

meridian

crossing

H = 12h

E

W

6

Z

0

At upper meridan crossing:

H = 0.

M

N

Example of hour angles

Ñ

1

2

3

4

5

11 10 9 8

7

SP

NP


Sidereal time: the hour angle of g

g

ST Hg

Horizon

W

S ST

Z

NP

M

SP

N


Sidereal day Z

SP

N

Interval for 2 succesive local meridian crossings

of g

Sidereal day 23h56m04s

E

W

Sidereal day 24h*00m*00s* * : sidereals

Sidereal

Midnight

Sidereal

Noon


Measuring the right ascension

at meridian crossing

NP

d

g

a

ST = Hg ST = a + H

At upper meridian crossing: H = 0

Then:

a = STMer.crossing

Horizon

W

H S

M

Z

SP Slide adapted from Prof. Boczko

Prof. Rama

Meridian

Circle at

Valinhos

Do it yourself: star in London with hour angle H = 3h & declination d = 15o?

PN

d Horizon

W

H S

M

Z

PS Slide adapted from Prof. Boczko

Do it yourself: star in London with H=3h, d=15o & a=1h30m, draw a

PN

d

g a

What is the sidereal time ST? Horizon

W

H S

M

Z

PS Slide adapted from Prof. Boczko

ST = 4h30m

Do it yourself: draw Orion as seen from São Paulo

(23.5° S, 46.6° W) at the meridian passage

32

-90

-80

-70

-60

-50

12

h

http://www.stellarium.org/

The Sky at OPD observatory

2013/03/22 18h

R.A. of the Sun? What time is it?

Which date?

Sky at OPD: altazimutal

2013/03/22 18h

+90

+80

+70 +60 +50

0

+40

+30

+20

+10

0

What are the coordinates

(A, h) of the Moon?

Where is the

celestial South Pole?

Sky at OPD: altazimutal + equatorial

2013/03/22 18h

Sky at OPD: equatorial

2013/03/22 18h

-20

-30

-40

-50 -60

-70

-80 -90

-10

0

6h

7h

8h

9h

10

h

11

h

12

h

1h

0h

Latitude = -22°30’

P.S.

Which are the coordinates (α, δ) of

the Sun & Moon ?

-90

-80

-70

-60

-50

12

h

h (pole) = |latitude|


2013/03/22 19h

-20

-30

-40

-50 -60

-70

-80 -90

-10

0

6h

7h

8h

9h

10

h

11

h

12

h

1h


P.S.

13

h

Which are the coordinates (α, δ) of

the Orion belt?


2013/03/22 20h

-20

-30

-40

-50 -60

-70

-80 -90

-10

0

6h

7h

8h

9h

10

h

11

h

12

h


P.S.

13

h

What is the hour angle (H) of Sirius?


2013/03/22 22h

-20

-30

-40

-50 -60

-70

-80 -90

-10

0

6h

7h

8h

9h

10

h

11

h

12

h


P.S.

14

h

13

h 15

h

At what time would be the meridian crossing of

the Southern Cross?

What is the R.A. and declination of Crux & a Cen?


2013/03/23 0h

-20

-30

-40

-50 -60

-70

-80 -90

-10

0

6h

7

h

8h

9h

10

h

11

h

12

h


P.S. 1

4h

13

h

15

h

16

h 1

7h

What is the sideral time?


2013/03/23 2h

-20

-30

-40

-50 -60

-70

-80 -90

-10

0

8h

9

h

10

h

11

h

12

h


P.S.

14

h

13

h

15

h

16

h

17

h

18

h

19

h

What is the R.A. of Scorpius' tail?


2013/03/23 4h

-20

-30

-40

-50 -60

-70

-80 -90

-10

0 10

h

11

h

12

h


P.S.

14

h

13

h

15

h

16

h

17

h

18

h

19

h

20

h

21

h

22

h

What would be the hour angle (H) of Arcturus at

05:00 in the morning?


2013/03/23 6h

-20

-30

-40

-50 -60

-70

-80 -90

-10

0

12

h


P.S.

14

h

13

h

15

h

16

h

17

h

18

h

19

h

20

h

21

h

22

h 23

h

What is the R.A. of the East point?

Campos dos Goytacazes, RJ http://www.twanight.org

http://apod.nasa.gov/apod/ap090509.html

Imagine the equatorial system on the sky!

http://www.twanight.org/

Ecliptic system

PNE

W

N

L

b

( ℓ , b ) 00 ℓ < 3600

(S) -900 b +900 (N)

ℓ : ecliptic longitude

b : ecliptic latitude

g

ℓ


Equatorial & Ecliptic System

NP

EPN

W

NP EPN

g

N

E

g

W


Galactic system ( ℓ , b )

© Astronomy Methods

ℓ b

Exemple drawing

50

Dec = lat

Zenith

Horizon

Astronomical coordinates and planning observations Ijorge/aga5802_2017/2017_05_coordenadas1.… · AGA5802 Astrofísica Observacional Astronomical coordinates and planning observations

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