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Constellation from SAO number?



 
 
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  #1  
Old December 5th 04, 10:23 AM
Giancarlo
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Default Constellation from SAO number?

Hello,

how can I tell the constellation where a star is, from its SAO number?
I mean: are there catalogs or lists or whatever that tell this?
I have a full SAO file but I can't see this information.

Of course, I may find out this information from the coordinates (RA
and Decl), but this would be very long (if I have hundreds of stars).

One question: coordinates change due to precession, but I understand
that the boundaries (of constellations) change either, so all the
stars remain in their constellation (if proper motion is not
considered - I am talking about precession only). Is it correct?

By the way, the only source where I can find the constellation of
SAO stars is a "star name seller". However, not all SAO stars are listed,
so this is not useful to me.
And I don't need to buy or to name a star in their database :-)

Thanks,

Giancarlo
  #3  
Old December 5th 04, 04:48 PM
William Hamblen
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On 5 Dec 2004 01:23:44 -0800, (Giancarlo) wrote:

how can I tell the constellation where a star is, from its SAO number?
I mean: are there catalogs or lists or whatever that tell this?
I have a full SAO file but I can't see this information.

Of course, I may find out this information from the coordinates (RA
and Decl), but this would be very long (if I have hundreds of stars).


Constellation boundaires are well defined. See
http://www.maa.agleia.de/Cat/Vol1/Constell/
for example. You then can program to figure which region of the sky a
particular right ascension and declination lies. I suppose someone
has written this program already.

  #4  
Old December 5th 04, 07:44 PM
Robert Sheaffer
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Giancarlo wrote:

Hello,

how can I tell the constellation where a star is, from its SAO number?
I mean: are there catalogs or lists or whatever that tell this?
I have a full SAO file but I can't see this information.


Actually, star constellation information is now available from my free
program RTGUI+S. I recently put it in.

You have to download the program itself, which is only about 540k, then
also the auxiliary catalog PPM, which contains SAO and HD numbers. The
PPM catalog for RTGUI is kind of large, containing 469,000 entries; it's
a 9.4 meg download, and expands to 47 meg when you use it.

Start up RTGUI, and switch the catalog to PPM.RTG. Then if we do a
"simple search" for SAO 12345 (a number I just made up), we get the
following:

PPM 13752, D +67 215, SAO 12345 ,HD 15784 ,Cas


www.rtgui.com



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Visit the Debunker's Domain - http://www.debunker.com
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  #5  
Old December 5th 04, 09:44 PM
David E. Francis
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Chris L Peterson wrote in message . ..
snip


One question: coordinates change due to precession, but I understand
that the boundaries (of constellations) change either, so all the
stars remain in their constellation (if proper motion is not
considered - I am talking about precession only). Is it correct?


Correct.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


Chris,

Have you forgotten about 10 Lyn and 41 UMa?

Francis
  #7  
Old December 5th 04, 10:16 PM
Robert Sheaffer
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Chris L Peterson wrote:

On 5 Dec 2004 01:23:44 -0800, (Giancarlo) wrote:

One question: coordinates change due to precession, but I understand
that the boundaries (of constellations) change either, so all the
stars remain in their constellation (if proper motion is not
considered - I am talking about precession only). Is it correct?


Correct.


Actually, constellation boundaries are tied to some fixed epoch. The
linked page implies that it's 1875. So I guess they need to rotate just
a bit. Only then they won't be nice north-south lines, but curves.


http://cdsweb.u-strasbg.fr/htbin/Cat?VI/42

The program to find the constellation originally comes from Roman N. G.,
Pub. Astron. Soc. Pac. 99, 695, (1987),=1987PASP...99..695R.



--
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Skeptical to the Max!
Visit the Debunker's Domain - http://www.debunker.com
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  #8  
Old December 5th 04, 10:27 PM
Chris L Peterson
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On Sun, 05 Dec 2004 13:16:44 -0800, Robert Sheaffer
wrote:

Actually, constellation boundaries are tied to some fixed epoch. The
linked page implies that it's 1875. So I guess they need to rotate just
a bit. Only then they won't be nice north-south lines, but curves.


Both constellation boundaries and star coordinates have to be precessed to the
current epoch (or the common epoch) before they can be used. That is why
Giancarlo is correct in his understanding that stars and constellations stay
together (proper motion excepted).

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
  #9  
Old December 5th 04, 10:50 PM
SaberScorpX
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Have you forgotten about 10 Lyn and 41 UMa?

That would be 41 Lyn and 10 UMa.
These stars are frequently singled out to show stellar motion and the overall
transient nature of constellation boundaries.
  #10  
Old December 5th 04, 11:03 PM
Giancarlo
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... You simply enter the
coordinates into a program that returns the constellation.
The program works by
comparing the coordinates against the precessed (from 1875.0 to B1950,
the SAO epoch) boundaries of the constellations.
The program is very short; if you'd
like a copy of the source code, let me know and I'll email it to you.


Thanks: my email is amor99 AT iname.com .
In what language is this code?
By the way, the epoch is 2000 (I have the transformed SAO coordinates).

Thanks,
Giancarlo
 




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