Re: Everything is Hotsy-Totsy Now

[Tom Droege <tdroege2@earthlink.net>]

At 11:01 PM 5/8/02 -0400, you wrote:
>   Don't be afraid to go back and re-reduce disks 4 and 5, testing
>some of the ways to answer the questions you've been asking (as I
>describe above).  You don't _have_ to keep looking at new data :-)
>
This is really the most important thing to do at this stage.  Just keep 
looking at the same old data with a critical eye.  Well, first I am looking 
at a bunch of data and asking the question "Is some data better than 
others?"  "Does all the data have the same flaws?"  Those kinds of 
questions.   Then I will worry about whether one can make some cuts.

For example, at the moment I am suspicious that the camera is not looking 
at clear sky at the beginning and end of a run.  Possibly only part of the 
field is obscured.

Possibly Michael can suggest what happens in this case.  For example, I 
know that if I try to look at too large a declination, that the V camera 
sees less light in the NE corner of the image.  (It is looking at the roof) 
As I understand it, Michael is doing aperture photometry.  That is, he is 
comparing the brightness of a star to a dark ring around it.  Now in this 
case, both the star and the ring get fainter.  But if it is then compared 
against the brightness of all the catalog stars in the whole field, it will 
seem too dim.  If it is only compared to the catalog stars that are nearby, 
then one might get a better measurement.  The same holds true for clouds 
(i.e. contrails) passing by that might be small compared to the field.

Tom Droege