Spotting Scopes
Spotting scopes are primarily used for terrestrial observing at low to medium magnifications with 20-60x zoom eyepiece being quite common. Most spotting scopes present an image that is both upright and right-left correct, which is desirable for terrestrial observing. The numerous prisms used to achieve a correct image reduce light transmission and also limit maximum useful magnification. These issues are of little concern in daylight terrestrial observing, but they do limit the usefulness of most spotting scopes for astronomical observing.
Also listed on this page are Maksutov-Cassegrain telescopes, which represent something of a crossover between the two worlds. These telescopes present an image that is upright but right-left reversed. These telescopes do not suffer from the limitations listed above.