Re: fun with co-adding images on Disk Set 19

[<aah@nofs.navy.mil>]

I was not dumping on PCVISTA (you know that, Michael!)  I just mention
iraf in most of these cases because (a) just about every possible
image processing step is available in iraf somewhere, and
(b) the documentation is reasonably good (and full source
code, too!) so it is a good place to turn when learning
about a particular algorithm.  Other programs can certainly do shift/add/rotate.
  It gets worse in many cases.  I created a 10-hour composite
of NGC6853 (M27), the planetary nebula, from several years of subarcsec
images taken for the 1.55m parallax program.  Unfortunately, there
were three different 2kx2k detectors used, so I had rotation/shift/
scalechange/distortions to remove.  IRAF has such tasks (geomap/geotran),
and is often used when comparing data from different wavelength regimes.
For TASS, you don't need anything that complex unless you want to
stack, say, the V&I frames together.
Arne