Catadioptric Telescopes

Catadioptrics use a combination of mirrors and lenses to fold the optics and form the image. There are two popular desgns: the Schmidt-Cassegrain and the Maksutov-Cassegrain. In the Schmidt_Cassegrain the light enters through a thin aspheric Schmidt correcting lens, then strikes the spherical primary mirror which reflects the light out an opening in the rear of the instrument where the image is formed at the eyepiece. Catadioptrics are the most popular type of instrument, with the most modern design, marketed throughout the world in 3.5" and larger apertures.

Schmidt-Cassegrain Advantages

• Best all-round, all-purpose telescope design. Combines the optical advantages of both lenses nd mirrors while cancelling their disadvantages.
• Excellent optics with razor sharp images over a wide field.
• Excellent for deep sky observing or astrophotography with fast films.
• Very good for lunar, planetary and binary star observing or photography.
• Excellent for terestrial viewing or photography.
• Focal raio generally around f/10. Useful for all types of photography. Avoid faster f/ratio telescopes (they yield lower contrast and increase aberrations). For faster astrophotography, use a Reducer/Corrector lens.
• Closed tube design reduces image degrading air currents.
• Extremely compact and portable.
• Easy to use.
• Durable and virtually maintenance free.
• Large apertures at reasonable prices and less expensive than equivalent aperture reflectors.
• Most versatile type of telescope.
• More accessories available than with other types of telescope.
• Best near focus capabiltiy of any type of telescope.

Schmidt-Cassegrain Disadvantages

• More expensive than Newtonians of equal aperture.
• Doesn't look like what people expect a telescope to look like.
• Slight light loss due to secondary mirror obstruction compared to refractors.

  

Maksutov-Cassegrain

The Maksutov-Cassegrain design is similar to the Schmidt with basically the same advantages and disadvantages but is not quite as good optically given the same focal ratios. It uses a thick meniscus correcting lens with a heavy curvature and a secondary mirror that is usually an aluminized spot on the corrector.

The Maksutov is heavier than the Schmidt and because of the thick correcting lens takes a long time to reach thermal stability at night in larger apertures (over 90mm).

The Maksutov optical design typically is easier to make and should be less expensive than the Schmidt-Cassegrain.

In summary a small reflector is the best general purpose telescope for beginners as they are good on all types of objects and for starting astrophotography.
See CELESTRON FIRSTSCOPE 114 EQ.
If you wish for the ultimate planetary telescope, and also a scope which is virtually maintenance free then look no further than a refractor. See FIRSTSCOPE 70 EQ.

If you’re looking for an advanced first telescope with a traditional German Equatorial mount or want to upgrade to a larger aperture telescope, consider the C8-S telescope. Mounted on the CG-5 EQ mount, both axes have precision worm gears for extremely smooth motion. Equipped with 2" steel legs, this heavy duty mount delivers jitter-free images. With adjustable height, the very rigid tripod has excellent damping characteristics and a convenient accessory tray/leg brace for added strength. See CELESTRON C8S