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The successful tests of Codes I and II reported in Paper II prompt
thoughts as to the scientific programs that could benefit from their
application. Some of these might be described as software-driven
observing programs.
Conventional deconvolution of images of QSOs does
not usefully contribute to morphological studies of host galaxies
because of the ringing centered on the deconvolved quasars. But with
Codes I or II, the quasar can be treated as a designated point source.
This not only eliminates ringing but also provides the restored and
regularized image (
) of the host galaxy with quasar removed.
With the alternative technique of PSF fitting and subtraction, the
residual image is not restored and also suffers from the Poisson noise
associated with the bright quasar and left behind on subtraction.
Major programs underway with HST aim to
discover Cepheids in relatively distant galaxies and thus to determine
using the locally calibrated period-luminosity relation. In these
programs, the HST resolves crowded fields into stars thus allowing
Cepheids to be discovered and photometered.
An alternative approach is the following: First, a single HST image
is used to resolve the field into stars and to determine accurate star
positions. Multiple ground-based images of the field are then
decomposed into stars using Codes I or II with the HST star positions
as input. Finally, from the values 
on the different
frames, Cepheids are discovered numerically and their periods found.
When so used, Codes I and II effectively transfer HST's resolving
power to ground-based telescopes. Besides thus being highly economical
of HST time, this technique has the further advantage that the
photometry is in well-understood systems established with and for
ground-based telescopes.
Many planetary nebulae and supernovae
remnants occur in extremely crowded star fields, to the point that
scientifically useful measurements are hard to make. Again Codes I or
II could be used with star positions from one HST image to obtain
star-free ground-based images of such nebulosities in
diagnostically-important emission lines.
Because of variable seeing,
conventional fixed-aperture photometric measurements of SNe are
contaminated with variable amounts of light from the host galaxy. But
with Codes I or II the SN can be designated as a point source; its
intensity is then determined relative to a detailed model of the host
galaxy with seeing taken into account.
Next: About this document
Up: Image Restorations of High
Previous: Code III: Regularized