Amateur telescope making

Before the advent of modern mass-produced telescopes, the price of even a modest instrument was often beyond the means of an aspiring amateur astronomer.

Between 1933 and 1990, Sky & Telescope magazine ran a regular column called "Gleanings for ATMs" edited by Earle Brown, Robert E. Cox, and Roger Sinnott.

The ready supply of surplus optical components after World War II and later Sputnik and the Space Race also greatly expanded the hobby.

The tester is adjusted so that the returning beam from the pinhole light source is interrupted by the knife edge.

Silver coatings have higher reflectivity than aluminum but corrode quickly and need replacing after a few months.

The mirror is aluminized by placing it in a vacuum chamber with electrically heated tungsten or nichrome coils that can evaporate aluminum.

Instruments built by amateurs have been employed in planetary study, astrometry, photometry, comet and asteroid discovery to name just a few.

Some amateur telescope makers build instruments that, while looking crude, are wholly suited to the purpose they are designed for.

For a given design the difficulty of construction grows roughly as the square [citation needed] of the diameter of the objective.

A 6-to-8-inch (150 to 200 mm) Newtonian is considered a good compromise size since construction is not difficult and results in an instrument that would be expensive to purchase commercially.

A 12-to-16-inch (300 to 410 mm) reflecting telescope is difficult, but still within the ability of the average amateur who has had experience building smaller instruments.

Amateurs have constructed telescopes as large as 1 metre (39 in) across, but usually small groups or astronomy clubs take on such projects.