Re: Tycho-2 catalog

[Arne Henden <aah@nofs.navy.mil>]

Ok, that star is listed in many catalogs, including the MarkIII tenx.
Note that it has Tycho2 Bt/Vt of 12.095/11.052, well outside my
normal cutoff of V=10.0 for Tycho2.  Michael has relaxed the reference
catalog requirements far beyond my limits, mostly to provide sufficient
astrometric reference stars.  As I stated in the Mark III days, for
photometric calibration you have to restrict yourself to stars
brighter than V=10 and within specified color limits (for accurate
transformation to the standard system).
   I don't think Michael has the option yet of using
a restricted subset of the refcat when doing the photometric calibration,
but that should be high on his list (or better yet, allowing for an
entirely different catalog for photometric calibration).
   Bottom line:  this star is too faint and too red to be even moderately
correct.  Give me another example where the star is bright and not
too red where you are getting comparable errors.
Arne

Tom Droege wrote:
> Sorry, it was .586.  A next project for me is to get the data processing 
> machine hooked up on the network to the internet.  Sigh!  I carry data 
> between the two machines on bits of paper.