AstroZap 254mm f/5 Newtonian Telescope OTA
OK, you’ve decided to check out Astrozap’s 6" 8" & 10" Newtonian reflector telescopes. In contrast to telescopes, reflectors use a large mirror to gather light and reflect it to a smaller secondary mirror which then directs the light to the focalplane. In astronomy, size does matter, and the chief benefit of a reflector is being able to get a larger telescope for the same or less money than a refractor or catadioptric. This is particularly true with the Newtonian design.
The Newtonian reflector configuration is the granddaddy of all reflector designs. Invented by Isaac Newton in the latter part of the17th Century (when he wasn’t busy inventing calculus) and unveiled in 1672, this system uses a spherical or parabolical curved concave primary mirror which gathers and reflects light back up the optical tube to a flat mirror that in turn redirects the light out of the side of the tube to the focal plane. Newtonian reflectors are particularly easier to make since only one optical surface, the primary mirror, has to be shaped (or, in astro-ese, “figured”). A prominent author of several books on telescopes and telescope making once described the 400 year old Newtonian design as providing the best value for the money. The reflector’s chief drawback is spherical aberration, astigmatism and coma, optical phenomena that cause stars and objects toward the edges of the field of view to undergo distortion. Like a radio that’s slightly out of tune, a fast Newtonian (f/6 or less) can exhibit these problems as a result of a lack of acceptable quality control in the figuring process. Another necessity is maintaining proper mirror alignment (“collimation” in astro-ese), which requires checking prior to starting an observing run. Also, the reflector’s secondary mirror can reduce contrast and obscure fine detail if it is too large.
Astrozap’s Newtonians will not disappoint. The fast f/4 and f/5 focal ratios provide awesome views of planetary and deep sky objects. These instruments are made with painstaking attention to detail in the mirror figuring process, which yields a field free of spherical aberration, astigmatism and coma.
Astrozap Newtonians are available as a complete telescope package or optical tube only. Finished in a high-gloss white coating, the OTA price includes the optical tube assembly, 8x50 straight finder, mounting rings and an aluminum dovetail bar. The complete telescope package price includes the OTA, 8x50 straight finder, mounting rings, dovetail bar, sturdy German equatorial mount with rigid tubular steel tripod, illuminated polar finder, upper and lower eyepiece trays, 20mm and 6.5mm plössl eyepieces and a 1.25" diagonal.
Take one to your favorite observing site and see for yourself why Newton’s design has stood the test of time and how well an Astrozap Newtonian Reflector will serve for years to come.
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