Re: A Question for Michael R.

[Stupendous Man <richmond@a188-l009.rit.edu>]

> Assume I am saving the corrected .fits file.  Now in the future I want to 
> rerun the pipeline using an improved photometry catalog.  Can it be 
> done?  

  Yes.  It's actually quite simple.  The only step you need to re-run
is the very last one, call "do_photom."  The procedure would be something
like this:

   a) if you have the .clt files on CD-Rom, put them in a work directory
         go to step m)

   b) if you have the .ast files on a CD-Rom, put them in a work directory
         run the "do_collate" step
         go to step m)

  c) if you have the .pht files on a CD-Rom, put them in a work directory
         run the "do_astrom" step
         run the "do_collate" step
         go to step m)
 
  d) otherwise, you need to start with the corrected FITS images
         run the "do_stars" step
         run the "do_astrom" step
         run the "do_collate" step
         go to step m)

  m) modify the photom.param file to point to the new photometric catalog
         run the "do_photom" step


  It's really, really easy if you have saved the ".clt" files, which
are basically instrumental magnitudes with calibrated positions
for all matched V,I pairs of stars.

  
> 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.

  All these are basically lists of stars.  They are all much smaller
than the images.  You could save all the .pht, .ast, and .clt files
if you want, and not need many extra CDs to do it.

> 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.  

  Right.

> 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.

  Correct.  If you have the corrected .fits files, you can do this.
If you have the .clt files, you can do this _very_ easily.


              Michael