Star Ware: The Amateur Astronomer's Guide to Choosing, Buying ...

So You Want to Buy a Telescope! 37
impacts on the world of amateur astronomy: the Schmidt-Cassegrain, the
Maksutov-Cassegrain, and, most recently, the Maksutov-Newtonian. For our
purposes here, the discussion will be confined to these designs.
Schmidt-Cassegrain telescopes. Take a look through practically any astronomy
magazine published just about anywhere in the world and you are bound
to find at least one advertisement for a Schmidt-Cassegrain telescope (also
known as a Schmidt-Cas or an SCT). As your eyes digest the ads chock-full of
mouth-watering celestial photographs that have been taken through these
instruments, you suddenly get the irresistible urge to run right out and buy
one. Don’t worry—you would not be the first to find these telescopes so appealing.
In the last few decades, sales of Schmidt-Cassegrains have outpaced both
refractors and reflectors to become the most popular serious telescope among
amateur astronomers. Though Schmidt-Cassegrain telescopes are available in
apertures from 5 inches to 16 inches, the favorite size of all is the 8-inch model.
Is the Schmidt-Cassegrain (Figure 3.5) the perfect telescope? Admittedly,
it can be attractive. By far, its greatest asset has to be the compact design. No
other telescope can fit as large an aperture and as long a focal length into such
a short tube assembly as a Schmidt-Cas (they are usually only about twice as
long as the aperture). If storing and transporting the telescope are major concerns
for you, then this will be an especially important benefit.
Here is another point in their favor. Nothing can end an observing session
quicker than a fatigued observer. For instance, owning a Newtonian reflector,
with its eyepiece positioned at the front end of the tube, usually means having
to remain standing—sometimes even on a stool or a ladder—just to take a
peek. Compare this to a Schmidt-Cassegrain telescope, which permits the
observer to enjoy comfortable, seated viewing of just about all points in the
sky. Your back and legs will certainly thank you! The eyepiece is only difficult
to reach when the telescope is aimed close to the zenith. As with a refractor
and a Cassegrain, a right-angle star diagonal placed between the telescope and
eyepiece will help a little, but these have their drawbacks, too. Most annoying
of all is that a diagonal will flip everything right to left, creating a mirror image
that makes the view difficult to compare with star charts.
All commercially made Schmidt-Cassegrain telescopes look pretty much
the same at a quick glance, but then again, so do many products to the uninitiated.
Only after closer scrutiny will the features unique to individual models
come shining through. Standard-equipment levels vary greatly, as reflected in
the wide price range of Schmidt-Cassegrain telescopes. Some basic models
come with an undersized finderscope, one eyepiece, maybe a couple of other
bare-bones accessories, and cardboard boxes for storage, while top-of-the-line
instruments are supplied with foam-lined footlockers, advanced eyepieces,
large finders, and a multitude of electronic gadgets. (As I mentioned before, if
you love widgets and whatchamacallits, then the Schmidt-Cassegrain will
certainly appeal to you.) Most amateurs can find happiness with a model
somewhere between these two extremes.
Another big plus of the Schmidt-Cassegrain is its sealed tube. The front corrector
plate acts as a shield to keep dirt, dust, and other foreign contaminants off