Re: Photometry

[Tom Droege <tdroege2@earthlink.net>]

This brings up the question as to whether I should also save the .pht, 
.coo, and .ast files.  They are relatively small.  Still, they can be 
reconstructed perfectly.  For study, one can just start with a test set of 
images, run then through once, and then play using the .coo, .pht, and .ast 
files as needed.  There are also the .clt files.

OK my feeling is still to keep stuff as near raw sky as possible.

I figure the following probabilities:

1) By far the most probable.  We want to look at a particular star and see 
if there is anything funny in the image.  For this purpose the files I am 
saving are the best.  You don't have to process them again to get a good 
looking image.  They look as nice as we know how to make them.  One can get 
pretty close to a star position.  I know what I have been doing when I am 
looking up "flasher" events.  I get out the image and position the cursor 
on the coordinates.  If I see *anything* near it (like a satellite track) I 
assume that it is the cause of the problem and discard the event as a 
possible flasher.

2) A possibility.  In the future we have a better reference catalog for 
photometry.  We want to reprocess the images to see if this improves the 
error.  For this the .ast, .coo, .pht, and .clt files save time but we can 
always regenerate them exactly from the corrected .fits files.

3) Zero possibility.  In the future someone with a time machine goes back 
and gets us better flats for a particular date and we want to use them to 
produce a better corrected .fits image.  I do not see any possibility of 
this happening.  I don't know where we could get better darks or flats in 
the future than the ones we have at the time the data is taken.  I am open 
to a specific example where there is anything we might do in the future 
where the corrected .fits files would not be satisfactory.

Tom Droege

At 08:18 PM 6/7/03 -0600, Robert Creager wrote:

>Hey Tom,
>
>But, as Arne mentions, if you keep the instrumental magnitude reduced
>from the frames, you can use different reference stars till
>you are blue in the face, and not have to re-reduce another frame.  You
>just re-calculate the color and zero point, and re-apply to the
>instrumental magnitude to get your calibrated magnitude.  dB's are
>wonderfull for this.
>
>Later,
>Rob