The reflector uses a large concave mirror at the bottom of the telescope’s optical tube to gather light and direct it to a focus up at the top of the tube, where a smaller mirror redirects it to an eyepiece at the side of the tube. Some beginners initially have trouble with the concept of viewing sideways at the top of the telescope tube. However, it is quite comfortable once you get past the inability to easily sight over the telescope tube to aim it as you can with the long barrel of a refractor.

The reflector’s larger light-gathering area can provide bright images of deep space objects that are too faint for any small refractor to see. And the reflector’s large aperture can resolve details within those objects with a precision no small scope can match – if the seeing is good.

For deep space observing, a Dobsonian-type reflector is very cost effective. With big mirrors to gather light, and inexpensive wood mounts, these new Newtonians have brought about the age of the “light bucket” in amateur astronomy. The deep space observer on a budget has never had it so good.

The penalty you pay for this performance is typically one of large size and weight – although not necessarily one of high cost, as reflectors traditionally cost the fewest dollars per inch of aperture of any telescope type.

Another penalty is diffraction. Light diffracted, or scattered, by a reflector’s diagonal mirror can reduce image contrast in lunar and planetary observing, masking subtle details compared with an unobstructed refractor image.

Because of the curved shape of their primary mirrors, all reflectors have coma – an optical defect in which stars appear triangular or wedge-shaped at the edge of the field. This is usually unobjectionable, however, since objects of interest are normally kept in the center of the field, where eyes and eyepieces are sharpest and coma is less of a factor.

In addition, unlike refractors, a reflector requires periodic recollimation or alignment of its optics, and its exposed mirrors mean that periodic cleaning will also be required. However, this maintenance typically averages only a few additional minutes of work per observing session.

These drawbacks aside, for serious visual observing of faint galaxies and nebulas, as well as for more-than-acceptable lunar and planetary observing, you’d be hard-pressed to equal, much less surpass, the excellent price-to-performance ratio of a Newtonian reflector. Reflectors have been a best-seller for over 300 years – and sheer value for the money is why.

Here are a few reflectors in different price ranges that make good first telescopes: Bushnell NorthStar 3” computerized go-to altazimuth, Celestron ExploraScope 3.1” tabletop altazimuth, Konus K114 4.5” equatorial, Meade DS2130 5” computerized go-to equatorial. There are another dozen or so choices in our reflector catalog.

REFLECTOR REPORT CARD
(used in excellent seeing conditions and with no light pollution; adapted from Astronomy Magazine):

E = excellent VG = very good G = good F = fair P = poor 3” to 4.5” reflectors: 0 Portability: E Ease of setup: VG Ease of use: VG+ Performance on the Moon: E Performance on comets: F Performance on double stars: VG Performance on galaxies and nebulas: F Performance on planets: VG E = excellent VG = very good G = good F = fair P = poor 6” reflectors: 0 Portability: G Ease of setup: VG Ease of use: VG+ Performance on the Moon: E Performance on comets: G Performance on double stars: VG Performance on galaxies and nebulas: F Performance on planets: VG E = excellent VG = very good G = good F = fair P = poor 8” reflectors: 0 Portability: F Ease of setup: F Ease of use: VG+ Performance on the Moon: E Performance on comets: VG Performance on double stars: VG Performance on galaxies and nebulas: VG Performance on planets: VG

Some observers may not be able to fit the long tube of a reflector or refractor. If space is an issue, maybe a compound scope would suit you best. Let’s take a look at the pros and cons of compound telescopes . . .