Charles Messier's Catalog of Nebulae and Star Clusters
Charles Messier was not a telescope designer, but he's represented here for contributing a list of targets that became one of the most commonly used tools available to astronomers, then 
and now.
His original purpose for creating the list has been largely forgotten. Charles Messier was a comet hunter who made entries in his journal whenever he discovered a bright object he couldn't identify, but was clearly not a comet. If an object was unusually bright and didn't move over a period of days, Messier listed it, eventually distributing his findings to other comet hunters, helping them to avoid wasting time on these apparently stationary objects that were later identified as diffuse nebulae, star clusters, planetary nebulae, galaxies and asterisms.
Virtually unknown to the general public, Charles Messier (1730 - 1817) is probably better known to the amateur star gazer today than any other astronomer in history. Most telescope owners are familiar with the Messier's catalog of deep space objects and their corresponding numbers. Ask any astronomer, amateur or otherwise, about "M31" and they will immediately recognize the reference to the Andromeda Galaxy.
Completing one's search for Messier's listed targets has become an invaluable learning excercise for novices. Especially in the days before goto telescopes and digital setting circles, to complete the search for all 110 targets was no small task. Every year there is a brief window (mid March through early April) when all of the objects can be seen within a 24-hour period from flat locations with little light pollution. Messier Marathons and competitions are held throught the world during this time.
1 - 25 | 26 - 50 | 51 -75 | 76 -110