Working on Data

[Tom Droege <tdroege2@earthlink.net>]

I have been working on the data.  That is why I have been quiet.
Programming is a struggle for me.  Sigh!

So far I have concluded:

1) Some of the data is clearly bad.
2) One can identify and remove "bad" data.
3) The result is only a slight improvement when measured by a sigma vs
mag plot.

My conclusion so far is that the effects from the way that the data is
taken are more important than the amount of "bad" data in the data
base..

Taking data tracking a frame produces data with fewer "outliers". Taking
data pointing at random spots in the sky produces the largest spread.

While tracking produces better looking data, I think it just masks the
problems with the absolute photometry.  OK, we are a long way from
absolute photometry.  If we take data moving the star image position in
the frame it shows up as a greater spread in the data.  I think this
better reflects how good the quality might be. I plan to continue taking
data this way even though I could try to look at fixed sky cells and
make the data look better.     

Yes, there are a few days whose removal will make everything look
better.  But their removal does not affect the overall statistics very
much.  Also, removal of a few days may make it easier for WS type
programs to find the true variable stars. One can delete data from the
data base or figure out how to make variable star finding programs that
are less sensitive to "outliers" in the data.  I prefer the latter.

I started this work thinking that I wanted to delete some data from the
data base.  My present thinking is that it would not improve the data
base very much, and some possibly valuable measurements would be lost. I
am still working, so my opinion might change.   

I still think that work is needed on the reference catalog and that will
provide the greatest improvement for the data.

Tom Droege