FAQ
Responses
If you haven’t done so, check out the other FAQs answered here first. Additional accessories include:
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A set of high quality eyepieces of varying magnitude and field of view.
A straight-through viewfinder such as a Telrad.
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A set of high quality, deep-space star charts such as Uranometria and Star Atlas.
There are a great variety of options for astro-imaging depending upon your interest and your budget:
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The easiest place to start is with a standard 35mm SLR piggy-backed on your telescope. You will need a scope that has accurate motorized tracking for this to be practical. A camera that does not (yes, does not) have an electronic shutter is best. Astro-photography requires very long exposures. You will go through a battery very fast, and there’s nothing more frustrating than having the battery die 30 minutes into an hour-long exposure! You will probably want a high quality wide-angle lens and a high quality telephoto lens.
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A relatively new practice is that of using a digital camera or video camera attached to your scope through the main lens. Excellent shots of planetary objects and some stellar objects are captured this way.
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If you are ready to make a greater commitment to astro-imaging, you may want to look at CCD imaging. CCD imaging uses the computer chip as the light-gathering device much as your digital camera does. The difference is that the cameras are especially designed and manufactured for the exacting requirements of astro-imaging.
CCD imaging has some advantages over film. The CCD is much more sensitive than film and ‘never gets tired.’ When film is exposed over long periods of time, it begins to change its chemical balance... it gets tired. This is called reciprocity failure and will ruin many hours of hard work behind the scope! It is also less sensitive to the effects of light pollution. The trade-off is that it requires more precision in the mount’s tracking ability and the quality of the telescope’s optics. Since the camera is attached to the main scope, it usually requires a ‘GoTo’ scope. A PC is needed to collect the images downloaded from the camera, and the resulting images must be digitally processed through specialty software designed for that purpose. The result, however, can deliver truly spectacular images with the right equipment, finely tuned and expertly processed!
Nebula refers to non-stellar objects that are composed of gases which are excited by the energy of nearby stars, and so we see them emitting a glow or nebulosity. There are several types, but almost all of them are the result of exploding stars which have reached the end of their life cycle and are returning their materials to the cosmos for re-cycling. In about 3 to 5 billion years our sun will create objects of this form.
Globular clusters have special significance. They may contain from several hundred thousand to millions of stars and are so concentrated as to be strongly bound to each other by their mutual gravitation. They typically contain the oldest stars in a galaxy and are generally concentrated toward the center of galaxies. They are believed to have been formed early in the history of a galaxy. Globular clusters can be spectacular objects easily resolved in smaller instruments.
Open clusters are a small grouping of stars, usually 100 or so, that are loosely bound to each other by their weak mutual gravitational attraction. They contain stars much younger than globulars, many still building new stars.
A binary os a pair of stars bound to each other by their mutual gravitation. Their paths are usually elliptical, revolving around a common center of gravity. Binary and multiple-system stars are more common than previously thought. Higher resolution telescopes and other means of identifying them are changing the scientific view of their occurrence.
The “M” designation is used to identify objects cataloged by the French astronomer Messier beginning around 1758. He observed these objects with a 3-inch telescope that was of less quality than today's cheapest scopes! Of course, he had the benefit of less light-polluted skies. Other objects are classified by different cataloging systems: IC for Index Catalogue, NGC for New General Catalogue, etc. These designations are important because all maps and astronomical references use these systems for proper identification.