There are many telescopes to choose from, but CCD imaging has certain requirements which can narrow the field of choices.  Other considerations will include portability, other uses (such as visual observing), and, of course, cost.

Don't Overlook the Mount

One definite requirement is a mount with a very accurate drive motor.  The telescope needs to be able to track very precisely so that the tiny stars in an image stay tiny and do not turn into big blobs!  Some telescopes come with a mount (such as the popular goto Schmidt-Cassegrain telescopes) and others can be purchased as an optical tube assembly and placed on a separate mount.  When choosing a mount for a telescope make sure it is capable of holding the telescope steady during an exposure.  If a mount has a rated capacity of 50 pounds, putting a 45-pound optical tube on it may work well for viewing, but is probably taxing the mount's capabilities for CCD imaging.  A 30-pound optical tube would be a better match.  It's much better to have a mount that is considered overkill.

Optical Designs

The telescope itself should be of good optical quality and mechanical tolerances should be tight.  Anything that wiggles when it is not supposed to can ruin an image!  Almost all types of telescope designs will work for CCD imaging, but some are better than others.  Many Newtonian telescopes cannot reach focus when a CCD camera is attached unless the placement of the mirror or focuser is adjusted (some specially-designed Newtonians avoid this problem).  Refractors are suitable, but for most applications only a highly-corrected (and very expensive) apochromatic refractor will suffice.  Inexpensive achromatic refractors, which suffer from color aberrations, have these aberrations exaggerated by CCD systems that are sensitive in wavelengths the human eye cannot see.

Many people choose a Schmidt-Cassegrain telescope.  This design is compact, portable, suitable for both visual work and imaging or photography, and is moderately priced.  The use of focal reducers or specially-designed telescopes (such as the HyperStar system) allow for either long-focal-length imaging (planets, moon, small deep-sky objects) or short-focal-length imaging (big nebulae, galaxies, star clusters, comets, and more).  For wide-field imaging, small apochromatic refractors (3"-4" in aperture) are popular as well.

For much more information on telescopes for CCD imaging visit the Equipment Basics section.

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