Celestia Forums

I need the RA, DEC and distance coordinates for 5 stars, in proper Celestia format :

- HD 41004
- 34 Psc
- Altair
-82 eri
-HD 144579

How can I find the coordinates used by Celestia ?

Go to this site:
http://cdsweb.u-strasbg.fr/viz-bin/VizieR?-source=I/239

click the top button there (I/239/hip_main) to take you to the main hipparcos catalogue.

In the "Query by Position on the Sky" box, enter the name of the star then press enter or click the "submit query" button to the right of that text entry box. (if you want galactic lat/lon as well, you can tick the "Galactic" box in the row underneath).

The results list several things. I think you want the numbers that are in red in the _RAJ2000 and _DEJ2000 boxes on the left (but you need to convert those to decimal coordinates). That said, Celestia might use the ICRS numbers for RA and DE (from the 1991.25 epoch) which are a few cells over to the right. Selden? Chris? Can you clarify on this at all?

Distance can be found by looking at the number in the Plx cell of the results. 3.26 divided by that number (in arcseconds, not milliarcseconds) is the distance in lightyears.

You should be able to find any star in Celestia's star.dat file using this method.

Evil Dr Ganymede wrote:Go to this site:
http://cdsweb.u-strasbg.fr/viz-bin/VizieR?-source=I/239

click the top button there (I/239/hip_main) to take you to the main hipparcos catalogue.

In the "Query by Position on the Sky" box, enter the name of the star then press enter or click the "submit query" button to the right of that text entry box. (if you want galactic lat/lon as well, you can tick the "Galactic" box in the row underneath).

The results list several things. I think you want the numbers that are in red in the _RAJ2000 and _DEJ2000 boxes on the left (but you need to convert those to decimal coordinates). That said, Celestia might use the ICRS numbers for RA and DE (from the 1991.25 epoch) which are a few cells over to the right. Selden? Chris? Can you clarify on this at all?

Distance can be found by looking at the number in the Plx cell of the results. 3.26 divided by that number (in arcseconds, not milliarcseconds) is the distance in lightyears.

You should be able to find any star in Celestia's star.dat file using this method.

Thanks a lot for the precious help

But I guess you really mean the Plx divided by 3.26, and not the reverse ? If I recall, 1 psc (parsec) = 3.26 ly.

Okay, the numbers are making a lot of sense now. Apparently, you are right, it is 3.26 divided by the Plx number, and multiplied by 1000.

Thanks a lot !

- HD 41004 = HIP 28393 => 140.3472461 ly
- 34 Psc = HIP 813 => 324.86752988 ly
- Altair = HIP 97649 => 16.77382360 ly
-82 eri = HIP 15510 => 19.767697 ly
-HD 144579 = HIP 78775 => 46.8563425 ly



plx = Parallax
pc = parsec
ly = Light year

http://cxc.harvard.edu/toolkit/precess.jsp
(RA, DEC)

bye