Re: Soliciting criticism

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

  Robert wrote:

> I'm hoping some of you have the desire to critique, and offer suggestion
> about the graphs here: http://robertcreager.mystarband.net/ .  The are all
> from Tom's data, night 2157 (from a few weeks ago).  As the graph titles
> imply, one is reduced from source extractor, and one from sps2x.

  It puzzles me that the two graphs are so different.  In one case,
the I-band data appear to have smaller scatter at a given magnitude;
in the other, the V-band data.  I would guess that there are significant
tweaks you can make to the parameters which control the software.
In theory, one might expect the same results from two programs running
on the same data, no?  

  I'm afraid I'm not familiar with either program, so I can't
suggest which parameters you might change, and how much.  Sorry.

  Here are my suggestions:

     - try to figure out why one piece of software does better on
             the V-band, and the other on the I-band.
             Perhaps one camera has sharper images, and one
             program's parameters turn out to work better on sharp
             images?

     - pick one set of results, both V and I.  For stars with >= 20
             measurements, calculate the Welch-Stetson statistic.
             Select those stars with very large values of this
             statistic, and make some light curves.  Some of the
             chosen stars will be contaminated by single bad 
             measurements -- ignore them.  Try to come up with 
             a way to pick out the stars which really do vary more
             than they ought to.  Then look:

                  trends versus position on chip?
                  trends versus color?
                  any matches to catalogs of known variable stars
                          in the area?

  That's what I'd do.

                                                Michael