![]() ![]() Newtonians came back into style in a big way in the 1980’s when telescope makers commercialized a design by the former monk and astronomy popularizer John Dobson. Dobsonian reflector telescopes (credit: Meade Corp.) Dobsonian Reflectors Another advantage of Newtonians: because mirrors reflect all colors of visible light exactly the same, reflecting telescopes have no chromatic aberration. But it’s not a big deal if the focal ratio is bigger than f/6 or so. This makes stars appear wedge-shaped at the edge of the field of view. Newtonians also have a type of optical aberration called “coma”. ![]() Newtonians also tend to be bulky, with tube lengths of 4-5 feet or more. The adjustment is not complicated, but it takes a little practice. Newtonian reflectors occasionally require adjustment of their optical alignment– especially if the scope gets bumped. ![]() A top-of-the line 4-inch refractor costs as much, or more than, a 12-inch Newtonian reflector, yet the reflector has 9 times the light gathering capability. A smaller secondary mirror reflects light out the side to an eyepiece. The front of the tube is open the mirror sits at the back of the tube. Some homemade reflectors even use glass from the discarded portholes of a ship! The layout of a Newtonian reflector. And since no light passes through a mirror, less expensive glass is used. įor a given aperture, Newtonian reflectors are generally the least expensive telescope because, unlike the lenses of a refractor, only one surface of a mirror needs careful figuring and polishing. His immensely practical design, now called the Newtonian reflector, is the main type of purely reflecting telescope in use today by amateur astronomers. He used a second small diagonal mirror to direct light out the side of the telescope to an eyepiece. Isaac Newton gets credit for inventing the first reflecting telescope in the late 17 th century. Reflecting telescopes (or reflectors) collect light using a curved mirror at the rear of the main tube rather than a lens at the front end. By choosing the right type of telescope you should be able to enjoy and get the most out of your stargazing hobby for many years.A Newtonian reflector telescope on an equatorial mount (credit: Skywatcher). Final TipsĬhoosing a telescope can seem daunting, but remember there are many great resources out there to help you make the right choice, including our in-depth telescope buying guide. In addition to combining the best qualities of both reflectors and refractors into one package, the price of catadioptric telescopes usually falls mid-way between that of a refractor and reflector. ![]() They are durable, highly portable, easy to use, and produce “right-side-up” images. This hybrid telescope comes in two main varieties known as either Schmidt or Makutsov after their designers. These are excellent for observing the moon, planets and binary stars, as well as deep-sky objects. Catadioptric TelescopeĪ compromise between these two types of telescopes is a hybrid telescope known as a catadioptric, which uses both lenses and mirrors. A good entry-level for amateur astronomers would be a 3.1-inch (80 mm) or more refractor. On the other hand, refractor telescopes can suffer from some chromatic aberration caused by using lenses, and they are generally more expensive to buy than reflectors. Pluses for refractor telescopes include “right-side-up” images, the ability to come to thermal stability quickly meaning low image distortion, and a sealed tube which means little maintenance is required. They are ideal for viewing larger, brighter objects such as the Moon’s surface, the planets, or viewing Jupiter’s moons. Refractor telescopes use lenses and are usually long and slim in appearance. A good entry-level for amateur astronomers would be a 4-inch (100mm) reflector. Other pluses for reflectors are that they are far cheaper to buy than refractors, are more portable, and their mirrors reflect all wavelengths of light the same, thus correcting for any chromatic aberration. This makes them ideal for viewing such deep-sky objects (DOSs) as nebulae, star clusters and galaxies. They are the instrument of choice for deep-space objects and wide-field viewing on account of their large apertures and superior light-gathering abilities. Reflector telescopes use mirrors and are usually short and wide in appearance. ![]()
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