Re: Ensemble analysis: "new variables"

[Stupendous Man <richmond@a188-l009.rit.edu>]

  I wrote:

> >   In fact, you can pre-process the Tycho catalog in the area
> >   of a particular image, and pick out the good ensemble stars in advance.
> >   You might even make up a separate catalog of "good" Tycho stars
> >   for this use...

  Tom asked:

> Is this not a multi-stage process?  One also has to eliminate the variable 
> stars from the Tycho catalog.  I assume that there are some that are not 
> (yet) known to be variable.

  Fortunately, the Tycho catalog is based on observations of stars many
times over the course of two years or so.  The catalog indicates which
stars appeared to vary over that period.  One can discard those stars
from the set used as comparisons ...

                                           Michael