Telescope Performance

Approximate specifications and performance limits of telescopes up to 30 cm in Aperture

Table of popular amateur telescope sizes, limiting visual magnitudes, approximate price points and use. Note, the limiting visual magnitude is a conservative determination based on a .5 cm average pupil size of a normal, fully dark-adapted eye, Pogson’s relation and 6th magnitude as the visual limit for the unaided human eye. The price point is an approximate retail price that provides basic visual functionality for the telescope. Additional accessories and adaptations may cause the price to change.

This table does not address angular resolution, the ability to resolve and observe fine detail of an extended object such as the moon, a planet or an extended, non-stellar object such as an emission or reflection nebula.

It should be pointed out that there is NO substitute for aperture when attempting to observe or image an object. Light gathering power, the ability to gather more light and thus, observe faint objects and the telescope’s resolving power, the ability to discern fine detail or structure, are functions of the telescope’s aperture: light gathering power and optical resolution are attributed only to the telescope’s aperture. The ability to discern fine detail and observe fainter objects or the same object with more clarity, is determined solely by the telescope’s aperture and nothing else.

In observational astronomy, there is NO substitute for aperture!

Many mistakenly believe that an expensive camera or imaging device can be a substitute for aperture. Nothing could be further from the truth! Optical resolution is NOT the same as the digital resolution of a camera or imaging device. An exquisite camera or expensive imaging device with megapixel resolution can only capture what is presented to it by the telescope at the imaging plane.