What are the differences between terrestrial spotting scopes and astronomical telescopes?
Terrestrial telescopes should be compact, portable and deliver a “correct image” – one that is right-side up and oriented from left-to-right as we see objects with the unaided eye. Astronomical telescopes must be longer to accommodate great magnifications and have the large apertures to gather as much light as possible from objects at enormous distances and often with low light levels. Astronomers do not require “correct images,” so special image-erecting optics are not as important for celestial observation.
