Frequently Asked Questions
Q: What is a catadioptric telescope?
A: A catadioptric telescope, also known as a ‘compound’ telescope, uses a combination of mirrors and lenses to increase the scope’s focal range and power while keeping weight, length and bulkiness to a minimum.
The most popular type of catadioptric telescope is the Schmidt-Cassegrain, used by amateur astronomers the world over. Based on Bernhard Schmidt’s original camera lens design, scopes with this configuration feature a corrector plate as the first optical element, which is then figured by placing a vacuum on the internal side, and grinding the lenses and mirrors to the exact specification and angle required to correct the spherical aberration caused by the primary mirror. Many variations of the Schmidt-Cassegrain configuration exist, but in general they can be divided into two principal design forms: compact and non-compact.
Q: What is a dobsonian telescope?
A: A popular choice among amateur astronomers and home telescope makers alike, this Newtonian telescope design (popularized by John Dobson in the 1960’s) is an alt-azimuth mounted telescope famous for its simplicity of design. Dobson, an amateur astronomer who felt that astronomy should be open to everyone, created a design using plywood, formica, porthole glass and other everyday materials that could be built in someone’s back yard.
The Dobsonian design is intended for the visual observation of "deep sky" objects, a requirement which needs the astronomer to relocate to areas with little light pollution. Dobsonian telescopes are designed to capture as much light as possible from as few sources as possible, which necessitates their large diameter and long tube length. The large aperture design makes the dobsonian ideal for viewing deep sky objects such as star clusters, galaxies and nebulas.
Q: What is a computerized telescope?
A: Basically, that’s what computerized telescopes do. Using co-ordinates and identification numbers fed in to the mount, computerized telescopes locate, track and record different celestial objects. Now, many astronomy purists decry these delightful ‘go-to’ machines, claiming that they take the art out of astronomy and that people who use them never really get to understand the mysteries of the cosmos, but as an entry in to the hobby they are a great (if relatively expensive) choice.
Q: Why do I need a spotting scope—what is it?
A: A spotting scope is, in essence, a hand-portable telescope fitted with a large objective lens, used for long-distance bird watching and basic astronomy. Normally used in conjunction with a tripod, spotting scopes are also normally fitted with a range of eyepieces to achieve different effects. Some also act as lens attachments for SLR cameras, and can be used for ‘digiscoping,’ using the extra zoom afforded by the scope to take very detailed long-distance images.