[Kstars-devel] Wrong epoch in stars data

[Massimiliano "Max Negro" Masserelli]

Il giorno mar, 14/08/2012 alle 09.51 -0500, Akarsh Simha ha scritto:

> I agree this is a serious problem! So could you tell me if only
> Hipparcos is affected, or is the entire USNO NOMAD on J1991.25? If I
> remember correctly, we had a separate Erik Hog Tycho-2 catalog, and
> Jason did a cross-match against Tycho-2 to separate out Tycho-2 from
> NOMAD.

Uhm. Sorry I'm not familiar with kstars internals: maybe you can direct
me on files/objects to have a look at? What I can say is that it seems
that all data contained in kstars/data/stars.dat is consistent with my
hypotesis (at least for the objects I was able to spot based on their
name. All those coordinates seem to be taken from Hipparcos data, and
are expressed in J1991.25 (stars and catalogue as published). For all
those, I have code (using libnova) and data converted to J2000. 
> 
> So it's unlikely that only Hipparcos stars are affected. I'd
> appreciate if you could shed some more light on the problem. It should
> be easy to change the epoch of the catalog. 

Can you identify objects taken from other catalogues? I suspect the
problem shouldn't arise on those, because IIRC other catalogues were
published with coordinates expressed in J2000, but checking should be
trivial: load star coordinates in calculator and confront those with
coordinates as reported by a search on Simbad
(http://simbad.u-strasbg.fr/simbad/sim-fbasic). 

They should match (or be at least close). :)

If you can direct me on where I can find those data, I'm willing to
crosscheck.

Thank you for your time.
-- 
Massimiliano "Max Negro" Masserelli <negro at interim.it>