Re: "A method for optimal image subtraction" on TASS WWW site

[Chris Albertson <chris@topdog.pas1.logicon.com>]

Stupendous Man wrote:
 This is the Postscript version.
> Perhaps this will help those who have been having trouble downloading
> a copy for themselves.

I have not yet finished reading the paper but so far it appears 
that the technique may let us do what Tom had suggested ages ago:
Directly compare the images from three offset cameras to see if
anything changed/moved.  It seems to cover the case where the PSFs
of the two (or more) images or unequal.  Conceptually the technique
seems intuitive (once someone else first thinks of it) but the
math is "nontrivial" and then their are the details.  A one minute
compute time is attractive too.  In fact if one were to use the 
Linux based driver you could perform this as a background task
as each image came off the camera.  The CPU spends 90% of its
time waiting on the A to D converter.  I could see where even
a "dumbed down" version of this could be useful for detection
of tracks of various types or single events like flair stars.
This type of stuff falls through our current system.  This
stuff is of interrest but we are just tosing it out now.
All you need to do is subtract the images then ring a bell if
there are any bright pixels.  Don't worry about automated
photometry, just sound the alarm (or more likely send and e-mail
notice).  People have said this method is "hard".  I think
only hard to get right.   A "dumbed down" version would be 
easier and maybe good enough for simply _detecting_ something.

I've made the paper more accessible
for those who have not yet install Ghostscript on their systems.
I made a text only version by use of an automated process.
No pictures or equations.  It is good enough for skimming.  You
will want the type-set equations and figures for detailed study.

Plain ASCII file is 28K long it is readable but needs proofing
and minor hand edits.  I have moved it to 
ftp.tass-survey.org/pup/incoming maybe someone will do the
proof/edit work.  It is best not to put it on a web page until
this work has been done.


--Chris Albertson

  chris@topdog.logicon.com                Voice:  818-351-0089  X127
  Logicon RDA, Pasadena California          Fax:  818-351-0699