RE: Tass Software Challenge

[Chris Albertson <chrisalbertson90278@yahoo.com>]

You say "...point me to THE software".  There isn't one.
There are as many as there are people looking at the data.
I'm sure you will find something you like but I doubt it
will be exactly what anyone else uses.

Tom's Tass Software Challenge is to send Tom something that
he likes and can use.  This is different from sending something
that works.  If not, any of a half dozen people here could "win"
with only the few minutes effort required to e-mail a www link.

I think the way to proceed is to first get something that 
works that you like and use.  To prove that your system works
you would have to reduce some data, write up what you did and
the results and post it here for all to critique and then
figure out how to package it so that someone else can duplicate
your work with out having to go through the learning curve you
did. 

If you are interested in doing photometry with IRAF look at
this  http://iraf.noao.edu/docs/photom.html
Unfortunatly you will need to read most of what is on the above.
You will also have to make a choice between synthetic aperture
and PSF fitting techniques.

Just in case anyone reading this does not already know, here are
the steps any software will need to perform.

1) Create a calibration dark frame, perhaps by combining may
dark frames.
2) Create a calibration flat frame
3) apply #1 and #2 above to all observation frames.
4) Extract a list of stars from each frame.  This is be the
"centroid" of each star in (x,y) pixel coordinates.
5) Compute instrumental magnitude for each star in list
6) By use of astrometric catalog compute (non-linear) transformation
from (x,y) to (ra,dec) for each image.
7) By reference to a catalog compute transformation from
instrumental to "standard" magnitudes.
8) Write out one starlist per image frame.

9) combine star lists so that observations of the same star
are "close" together.  Maybe sort on a "name" that to give
to each star.

10) merge "combine star lists" (#9 above) from multiple runs
and multiple TASS sites into one big list (I would us an RDBMS)
and make the data available over the Internet.

Tom has asked for only steps 1..8 or 9.

I think you will find that the details of how best to perform
any of the above steps can be endlessly debated.  That's one
reason you will not find "THE Software" for data reduction.

For example I think this
http://iraf.noao.edu/scripts/irafhelp?ccdproc
(scroll down to the section called "description.)
does a good job of steps up to #3

next look at 
http://iraf.noao.edu/scripts/irafhelp?digiphot and deside
if you like appphot or daophot either will get you
to step #5.

 


--- Bill OConnor <wtoconnor@mmrsoftware.com> wrote:
> Ok, I have the data set.  I've looked over the FITS website.  Can
> anyone
> point me to the software that is currently used to process data.  I
> assume that it runs on some flavor of *nix. Tom mentioned IRAF.  
> 
> I have downloaded a copy of Bohdan Paczynski's paper but have not had
> time to really look at it. Is there anything else I should be looking
> at?


=====
Chris Albertson 
  Home:   310-376-1029  chrisalbertson90278@yahoo.com
  Cell:   310-990-7550
  Office: 310-336-5189  Christopher.J.Albertson@aero.org

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