2 months to go: time to be serious about observing run preparations
Feb 24, 2016
2 months to go: time to be serious about observing run preparations
getting ready for our (any!) observing runhtt
p://cheezburger.com/5797953792
http://glozing.blogspot.com
/2012/09/like-scouts-say-be-prepared.html
http:
//la
bass
lix.c
om/b
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YOU THE OBSERVER should never be the cause of this:
What is the scientific goal?
or …
how did we manage to fool the telescope allocation committee?
questions you should be able to answer• do I know what the point is?
– what astrophysical idea is being considered?– could I explain it to children, friends, other science teachers?
• do I understand if my telescope/instrument can attack this?– have I assembled a reasonable list of stars (or nebulae/galaxies)?– can I observe any/all of these objects?
• observatory location; time of year?• appropriate magnitudes?
• am I comfortable with magnitudes and colors?• can I translate from target star coordinates to where they are in the sky?• do I understand my telescope?
– basic optical configuration?– startup/shutdown, moving between targets, tracking targets?– dangers: mechanical limits of telescope; weather restrictions?
• do I understand my instrument?– optical design (not trivial for our instrument)?– what are its “parameters” (how faint can it go, at what spectral resolution, at what noise level)?– can I tell by looking at an output image whether I have done something stupid?– how do I save the data safely?
• can I interpret a spectrum that is obtained?– what does “interpret” really mean when I am sitting at the telescope at 4AM
• do I know the stuff to be done after the observing run?– extraction of a “clean” spectrum?– analysis to get desired results?
http://astronomy.sci.ege.edu.tr/ASTRO
-WEB/TR2/
fredhtt
p://astronomy.ege.edu.tr/gstars.izm
ir2013/index.html
fredEge University is in
Izmir, near the western edge of Turkey
Izmir is located in the Aegean province, which, of all the seven geographical regions of Turkey, enjoys the finest climate. In population it is the third city in Turkey.It is located in an area whose magnificent history has made it a tourist centre. It lies at the centre of the most important land, air and sea communication network in the ancient Aegean region.
In June we are observing red giant stars
http://nothingnerdy.wikispaces.com/E5+STELLAR+PROCESSES+AND+STELLAR+EVOLUTION
Thumbnail sketch of stellar evolution
http://nothingnerdy.wikispaces.com/E5+STELLAR+PROCESSES+AND+STELLAR+EVOLUTION
Hydrogen fusion powers most stars
http:
//sp
ot.p
cc.e
du/~
aodm
an/p
hysic
s%20
122/
end%
20of
%20
mai
n%20
sequ
ence
/end
ofm
ains
eque
nce.
htm
The alternate way of H-fusion interests us morehtt
p://
ww
w4.
nau.
edu/
met
eorit
e/M
eteo
rite/
Book
-Glo
ssar
yC.h
tml
Supposed to do the same thing: four H nuclei fuse to form one He nucleus + energy
Cycle doesn’t complete every time; net result is buildup of 13C and 14N
These products get mixed to the stellar surfaces as stars age to become red giants
C and N atoms form molecules, like CH and CN
We can observe these molecules in cool stars, and so we can check out enhancements in N and depletions in C and changes in 12C/13C ratios
The red giant clump is really well-known and understood
http:
//w
ww
.ast
ro.p
rince
ton.
edu/
~bp/
Remember: color is temperature, andabsolute magnitude is luminosity
http:
//six
days
cien
ce.c
om/c
urric
ulum
/tex
tboo
ks/c
hapt
er-1
1/
The red giant clump is really well-known and understood:here is a color-magnitude diagram for nearby stars
http:
//w
ww
.ast
ro.p
rince
ton.
edu/
~bp/
main sequence subgiants
Red giants
The red giant clump is really well-known and understood:so, so … what are these things?
http:
//w
ww
.ast
ro.p
rince
ton.
edu/
~bp/
main sequencesubgiants
Red giants
For very old, low mass stars the clump spreads hotter into the “horizontal branch”
MSTO = main sequence turn-off; RGB = red giant branch; RHB = red horizontal branch; BHB = blue horizontal branch; BSS = blue straggler stars; FG = foreground (ignore)
De Boer et al. 2011, A&Ap
where the red giant clump should be
A simple question, too long ignored: why are there apparently so many bright RHB stars in the young disk
population surrounding our Sun?De Boer et al. 2011, A&
ApRGB clump
our target RHB stars
the task: identify true giant stars that are a few hundred K warmer than they should be, and do a detailed analysis of them to see if chemical clues can uncover their secrets …
We will also be studying red giant chemical compostions of open clusters
http:
//m
essie
r.sed
s.or
g/xt
ra/n
gc/n
0869
.htm
lhtt
p://
ww
w.a
tlaso
ftheu
nive
rse.
com
/ope
nclu
s.ht
ml
Most open clusters have only a few RGB stars, and it is tough to pick out cluster members from the general Galactic field population
http://www.starobserver.eu/openclusters/hyades.html
Melike is in charge of assembling the target listHer summary of the selection process, and my comments in blue:
The stars we are interested in are RHB stars.
First we did a literature scan and learned about our stars, finding out what temperature and absolute magnitude/luminosity range they have (location on the HR-diagram). We had to understand how temperature and luminosity (theoreticians’ units!) translate into colors and magnitudes (observers’ units!).
Then we used this information to sort out the catalogs, mainly using SIMBAD and HIPPARCOS. These were our basic star information sources.
We threw out the stars outside the temperature and luminosity range (if available) that we are interested in. This is an imperfect process, with uncertainties in all published quantities! We knew that some promising targets would turn out to be duds.
In our case, the Galactic latitudes of the stars are also important since we want to observe stars in the Galactic thin/thick disk and halo.
We used both spectral type and V-K color index in order to determine the temperatures. We also calculated the absolute magnitudes when the distance information was available. As always in astronomy, lack of accurate distances for every target is the biggest limitation for us.
photometric bandpasses? Most of us are familiar with the “UBV” system
http://w
ww
.asahi-spectra.com/opticalfilters/johnson_bessell.htm
lremember for example: V = mV, that is the apparent magnitude in the “visual” (yellowish) bandpass, close to the human eye response
we also used infrared “K” magnitudes
when available
the colors B-V, V-I, and especially V-K are good indicators of temperature
and the V (= mV) magnitude, IF YOU KNOW THE DISTANCE (PARALLAX) can be translated into absolute magnitude MV
http://coursewiki.astro.cornell.edu/Astro4410/BasicObservationalKnowledge
http://simbad.u-strasbg.fr/simbad/sim-fsam
http://simbad.u-strasbg.fr/simbad/sim-fid SIMBAD
HIPPARCOShttp://www.rssd.esa.int/index.php?project=HIPPARCOS
an actual star we need to observe in June!
¡Ay, caramba! Star names can be a headache
RA, Dec, KT, UT, LST, HA
https://dept.astro.lsa.umich.edu/ugactivities/Labs/coords/index.html
http://astunit.com
/astunit_tutorial.php?topic=time
first point of Aries = Vernal Equinox
RA = right ascensionDec = declinationUT = universal (Greenwich) timeLST = local sidereal timeHA = hour angleKT = kitchen (o’clock) time
Galactic coordinates
http://www.atlasoftheuniverse.com/galchart.html
Visualizing Galactic coordinates
http://starplot.org/docs/ch1.html
http://people.physics.carleton.ca/~watson/Physics/Astrophysics/4201_essentials/4201_coordinates.html?id=0
Our Smith Telescope at McDonald Observatory
30.6714° N, 104.0225° W
http://www.laurenceparent.com/portfolios/Texas/lptxmcdonaldob.html
https://webspace.utexas.edu/tsc494/site/autobio/m
ain.html
http://w
ww
.ira.inaf.it/Library/slides-archive/page20.html
Summary of 2.7m Smith Telescope properties
http://www.as.utexas.edu/mcdonald/facilities/2.7m/2.7.html
http://www.as.utexas.edu/mcdonald/facilities/2.7m/2.7.html
The desire is for spectra of our targetswe’ve all seen general stellar spectra before
http:
//pr
ance
r.phy
sics.
loui
svill
e.ed
u/cl
asse
s/10
7/to
pics
/ste
llar_
spec
tra_
exam
ples
/
HαHβHγHδ Na I “D”
Mg I “b”CH “G”
Reminder of basic spectrograph design
http://outreach.atnf.csiro.au/education/senior/astrophysics/spectrographs.htm
l
Echelle spectrographs are a bit more complex
http://www.ucolick.org/~vogt/hires.html
A solar echelle spectrum
http://www.noao.edu/image_gallery/html/im0600.html
A solar echelle spectrum
http://www.noao.edu/image_gallery/html/im0600.html
Telluric O2
Hα
Na I “D”
Mg I “b”
CH
Hβ
Hγ
Our spectrograph: the Tull echelle
circa 1968?? left to right:Harlan Smith, Gerard de VaucouleursBob Tull, Terry Deeming, Frank Edmonds
Very complex drawings designed to make you stop asking questions
What you will see at telescope
http:
//w
ww
.ast
roge
o.va
.it/a
stro
nom
/spe
ttri/
eche
lle_e
n.ph
p
Telluric O2
Hα
Na I “D”
Which you can “display” thusly:
Reduction and analysis: to be continued …
HELP!
http:
//se
arch
netw
orki
ng.te
chta
rget
.com
/fea
ture
/Tec
h-su
ppor
t-I-fo
rgot
-my-
pass
wor
d
TELESCOPE: http://nexus.as.utexas.edu:8081/obs_sup/man/manuals/TCS/tcs_quick_guide.html
SPECTROGRAPH: http://nexus.as.utexas.edu:8081/obs_sup/man/manuals/2dcoude.html
NIGHT REPORT: http://198.214.229.50:8081/cgi-bin/obs_sup/xrep_form.cgi
WEATHER: http://observatories.hodar.com/mcdonald/
fred