Analyzing Data

[Tom Droege <tdroege2@earthlink.net>]

Since I did not get data last night, I spent some time this morning looking 
at data I took on August 2.  A first look had found just 3 variable 
stars.  This applying WS and looking at those with large statistic.  > 10 I 
recall.

This morning I reprocessed the data and looked at WS > 1.  I found 13 
pretty likely variables.  One with a WS statistic of 1.2.

When I send out data sets, they contain a number of evenings of 
observations for each star.  This causes WS to generate big numbers for 
what amounts to day to day variations, or for long term variation.  This 
swamps the short term variations, so if you look at the data the way I have 
passed it out, it is hard to find the short term variables where the 
variation is small.

I started thinking about this when I noticed that we were finding mostly 
variables abound mag 10 and lower.  There should be more around mag 
11-13.  So why was I not finding them?

The answer is that they are there, one just has to look carefully with 
something better than WS.  OK, Doug has done a good job getting us a start, 
but something more is needed, I think.  We need a way to look at the data 
with WS over 1 and see what I can see if I look at it by eye.

Sometimes there is a big WS statistic and one look shows it is due to 1 bad 
point.  Well, it may be real, but not likely.  Mostly stars are not 
expected to brighten .2 mag for one measurement point.  So one can throw 
such things out.  But something has to look and see what is happening.

I think there is a lot of work to be done to develop better algorithms to 
find the variables.

Tom Droege