[Kstars-devel] Re: Poor quality of data in kstars main catalog?

[Akarsh Simha]

On Sun, Apr 10, 2011 at 02:28:34PM +0200, Massimiliano "Max Negro" Masserelli wrote:
> I'm in the process of introducing kstars to a local observatory for
> telescope control. While testing accuracy, I found some problems in
> pointing (with a 2000mm reflector with 40cm mirror). So I started
> looking at coordinates stored in catalog, and found "many" errors.
> 
> In particular, Arcturus (alp Boo) has RA 14 15 40.35 Dec 19 11 14.17
> J2000. If you have a look at simbad
> (http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=arcturus&submit=SIMBAD+search ) you'll see it should have RA 14 15 39.6720 Dec +19 10 56.677. I then looked at Hipparcos via Vizier (http://vizier.u-strasbg.fr/viz-bin/VizieR-S?HIP%2069673) and found that it shows the same coords as kstars, only in J1991.25 epoch (last batch of data on page, as follows):
> 
> ...
> RAhms	14 15 40.35	 	Right ascension in h m s, ICRS (J1991.25) (H3)
> (pos.eq.ra;meta.main)
> DEdms	+19 11 14.2	 	Declination in deg ' ", ICRS (J1991.25) (H4)
> (pos.eq.dec;meta.main)

Most of our star data comes from Tycho-2 and USNO NOMAD. So that means
that we got the epoch wrong? So what we thought are J2000.0 data are
actually J1991.25 data?

This should not be very hard to fix once I get the star catalogs back
on my database.

> I tried with a few other objects, and many were in the same conditions,
> save a few (Albireo, at least, as you can see in
> http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=albireo&submit=SIMBAD
> +search ).

> Deep sky objects seems inaccurate, too, but I wasn't able to find an
> hint on why...

Deep Sky Objects are in general inaccurate in KStars. Do you have any
suggestions for a standard Deep Sky catalog that is accurate and free
(as in distributable under terms of the GNU General Public License)?

We are allowed to redistribute the Saguaro Astronomy Club's database,
which is an amateur-compiled database with a lot of observational
details etc. I plan to merge our NGC / IC database with the broader
and more accurate SAC database.

If you have something more accurate than SAC, that would be great.

Regards
Akarsh