ABSTRACT
Telescope and mount comparisons are a popular subject covered in many general astronomy books, Douglas Adams favorite is 'Stargazing with a Telescope', by Robin Scagell, which evaluates the essential equipment for astronomy. All telescopes use glass lenses, mirrors or a combination of both. Glass and mirrors systems have unique pros and cons. The first telescopes were refractors, made from a positive primary lens and a negative eyepiece lens and produced an upright image. The German Equatorial Mount (GEM) is compatible with both refractor and reflector telescope designs and has the useful capability of simple polar alignment through a polar scope, aligned with its motor axis. Most refractors have built in dew-shields and Newtonian designs without a glass corrector plate have their optics at the base of a long tube which effectively shields the primary mirror. Dew heater tapes are the most common method to gently heat optics.
