[Kstars-devel] Star coordinate inaccuracy -- Hipparcos Epoch bug

[Massimiliano Masserelli]

Il 19/03/2013 09:45, Akarsh Simha ha scritto:

> Massimiliano made this offer earlier -- I'd be grateful if I could get
> replacement J2000.0 RA/Dec for all affected stars, under freely
> distributable terms.

I think the error derives from old stars.dat, that has been somehow 
"compiled" into data kstars is using now. I already provided a copy of 
stars.dat with coordinates corrected using novas-c library 
(http://aa.usno.navy.mil/software/novas/novas_c/novasc_info.
I think this corrected file has been committed into kstars current 
sources, the only problem is that it isn't referenced anymore in any of 
the other source files...

> However I can also find bright stars that are unaffected. In any case,
> it would be good to have a reliable list of stars' coordinates, that I
> can use to patch the star catalogs and release them.

Yes, I noticed that too. I think that depends on sky position and little 
proper motion. In the corrected stars.dat those stars haven't moved a 
lot, as expected.

> OTOH, I noticed that from your mail sometime in 2011, you point out
> that deep-sky catalogs are problematic too.

That was when I first noticed coordinates problem, and I blamed 
(incorrectly) deep sky catalog: the telescope I'm using at the local 
observatory has relative encoders, so we point at a bright star, sync 
and and then move to desired object. When pointing at faint objects, I 
noticed the accuracy of slew was poor, but the errors in bright stars 
catalog explain perfectly well the problem. :)

Sadly, due to this lack of accuracy, we had to switch kstars in favor of 
skychart, which by the way has a sound support for custom and online 
catalogs that I've started to fall in love with.
-- 
Massimiliano "Max Negro" Masserelli