PROCESSING THE IMAGES
A generation ago, the only way you could take an astronomical photo was
to expose a piece of film for a very long time, so time exposures hours
long were often required just to make an object visible. Today’s
amateur, armed with a digital camera (or CCD camera) and computer can
effectively create a long exposure photograph by taking a series of short-duration
photos and “stacking” them in the computer. In effect, the
computer adds all the light from all the photos together to form one image.
This significantly reduces the requirements for big, heavy, mounts, and
makes it possible for people with only a modest telescope, camera and
a computer to get photos that rival the big observatories of a generation
ago. These stacking programs, which often are free with the astrophotography
cameras, automatically “register” each image when stacking
to keep everything sharp. If one of the photos is blurred, it can be discarded
before stacking to result in a better final image.
After stacking, Image Processing programs, like Adobe Photoshop, or Maxim
DL, can be used to enhance contrast, color, sharpness, grayscale, and
other characteristics of the final image.
Note that these techniques can also be used on Solar System photography
and there are some photographs out there, taken with small scopes, that
look almost as good as the photos taken with orbiting spacecraft. Today’s
techniques for producing photos have truly resulted in some wonderful
advances in the quality of astrophotographs taken by amateurs.