Catadioptric Telescopes use a combination of the best features of reflectors and refractors into one package, giving you what many believe the best all-purpose telescope design. They combine the optical advantages of both lenses and mirrors, while avoiding there disadvantages. They allow the performance of large apertures to be folded into a small reasonably lightweight and portable package making for a short setup time.
There are two popular designs of these catadioptric scopes, the Schmidt-Cassegrain and the Maksutov-Cassegrain. The difference between the Schmidt Cassegrain and the Maksutov-Cassegrain is in the shape and size of the corrector plate (lens) at the top of the telescope. The Maksutov-Cassegrain uses a heavier, more complex corrector plate making them generally the more costly of the two, but also gives them better image quality.
Catadioptric’s are excellent for deep-sky observing, astrophotography, and terrestrial viewing. In addition they do very well for lunar, planetary and binary star observing. The main drawback as you would expect is the cost, an 8″ Schmidt-Cassegrain costs 50% to 300% more than an 8″ reflector (although about the same as a 4″ refractor).
Below is a breakdown of advantages, disadvantages, and performance ratings of catadioptric telescopes to help in your decision making. The information is borrowed from an article called Why buy a reflector? at Astronomics.com. An excellent place to go and do research and Buy a Telescope. The Catadioptric report card ratings are based on a telescope being used in excellent viewing conditions and with no light pollution. The data was a adapted from Astronomy Magazine. E = excellent; VG = very good; G = good; F = fair; P = poor.
Advantages:
- Best all-purpose telescope design, combining the optical advantages of both lenses and mirrors, while canceling their disadvantages
- Excellent optics with razor-sharp images over a wide field
- Excellent for deep-sky observing or astrophotography with fast films or CCD imagers
- Very good for lunar, planetary and binary star observing or photography
- Excellent for terrestrial viewing or photography;
- Closed-tube design reduces image-degrading air currents
- Compact and portable
- Easy to use
- Offer large apertures at reasonable prices less expensive than equivalent-aperture refractor designs
- Greater accessory availability than is the case with other types
- Best near-focus capability of all designs.
Disadvantages:
- More expensive than reflectors of equal aperture;
- It is not what people expect a telescope to look like
- Slight light loss due to obstruction by the secondary mirror.
Small aperture (3.5″ to 5″) Schmidt- and Maksutov-Cassegrains:
- Price range: $500-$4300
- Portability: E
- Ease of setup: VG
- Ease of use: G+
- Performance on the Moon: E
- Performance on comets: F
- Performance on double stars: G
- Performance on galaxies and nebulas: F
- Performance on planets: G
Medium aperture (6″ to 8″) Schmidt- and Maksutov-Cassegrains:
- Price range: $1000-$4000
- Portability: VG
- Ease of setup: VG
- Ease of use: VG+
- Performance on the Moon: E
- Performance on comets: G
- Performance on double stars: VG
- Performance on galaxies and nebulas:, G
- Performance on planets:, G
Large aperture (9″ to 16″) Schmidt- and Maksutov-Cassegrains:
- Price range: $1700-$20,000 and up
- Portability: P+
- Ease of setup: F
- Ease of use: G
- Performance on the Moon: VG
- Performance on comets: VG
- Performance on double stars: VG
- Performance on galaxies and nebulas: VG
- Performance on planets: VG
Catadioptric Telescope Recommendations
