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#1
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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
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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
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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 -- Robert Sheaffer - User name "Roberto" at debunker-dot-com Skeptical to the Max! Visit the Debunker's Domain - http://www.debunker.com Resources Debunking All Manner of Bogus Claims Also: Skepticism / Astronomy / Opera / more |
#5
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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 |
#6
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#7
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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. -- Robert Sheaffer - User name "Roberto" at debunker-dot-com Skeptical to the Max! Visit the Debunker's Domain - http://www.debunker.com Resources Debunking All Manner of Bogus Claims Also: Skepticism / Astronomy / Opera / more |
#8
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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
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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
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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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