Re: Data Cleaning

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

I may have missed something along the way.  If you remember way
back when, I posted software for the Mark III system that would
do inhomogeneous ensemble photometry for variables.  It would seem
that the logical thing to do for those stars that are obvious
variables in the Mark IV dataset is to forget about the frame-to-frame
zeropoint determination, which makes mistakes, and just do local
calibration for those stars using such an ensemble approach.  Has
this been done?  Get decent light curves and worry about absolute
photometry later.
Arne

Thomas Droege wrote:
> The weather looks awful for the near future so I am trying schemes to clean
> the data.
> 
> It appears that it is possible to improve the data by cleaning it by a
> relatively simple and unbiased (I hope) cut.
> 
> The result is not that the data looks much better on a sigma mag plot, but
> that it is easier to pick out the variables if there are not so many
> "outliers".
> 
> Progress is being made.  The present plan puts a number in the V flag
> position that contains the fraction of "bad" points in the image that
> contains the particular measurement.  How can one tell a bad point?  Well
> it is not possible to detect a single bad point.  One can only pick out
> points that are away from the norm for a particular star.  One expects a
> small fraction of points away from the mean in an image because some stars
> are variable.  However images with a large fraction of their measurements
> away from the mean are probably "bad" while images with a small fraction
> are probably "good".  Putting the fraction of bad points in all the data
> lines allows a user of the data to set his own cut.  
> 
> Stay tuned, boys and girls, for the first time I am making progress in
> "cleaning" the data.
> 
> Tom Droege
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