Don't Buy a Big Telescope!
By the Astronomy and Photography Online Staff
The Celestron C6, an excellent telescope. Illustration courtesy of Celestron International.
This article is directed at novice astronomers, meaning amateurs buying their second telescope (or first "serious" scope) after discovering that their initial instrument, probably a 60mm refractor or cheap table top Newtonian, lacks sufficient light grasp for viewing many deep sky objects. It should also serve as a warning to more experienced astronomers getting back into the hobby after a significant lay off: scopes have gotten bigger while you were away!
Let's get "big" defined from the outset. In terms of portable astronomical telescopes, the heaviest optical tubes should weigh no more than about 20 pounds (assembled). They should be sufficiently compact to fit in the trunk of an ordinary sedan and fit on mounting systems that can be transported and assembled quickly by one person without physical strain. While mentioning mounts, whether equatorial (EQ) or alt-azimuth (AZ), they should have precise slow motion controls that allow accurate and easy alignment of the scope with objects in the night sky. The biggest scope in the world is useless if you cannot accurately point it at a target and keep it there as the earth turns.
There is a trend in recent years for novice astronomers to go overboard and purchase very large telescopes. (Anything with an aperture exceeding eight inches is very large for our purposes.) Seeking to remedy a lack of light grasp, they err in the opposite direction and buy a telescope that is too complicated to assemble and collimate, too big, clumsy, heavy and difficult to transport. They exacerbate the problem by accepting a crude AZ mounting system, often made of wood and lacking slow motion controls or any method of precisely tracking celestial objects.
We recently heard about a novice who purchased a 16" truss-type Newtonian refelctor. This particular scope comes with a wooden Dobsonian mount without any slow motion controls or tracking capability. The assembled optical tube weighs 74 pounds and the mount weighs 54 pounds. It must be completely disassembled for transport and reassembled before use. After assembly, the primary and secondary mirrors should be collimated, a laborious procedure, especially for a novice. It would be hard to imagine a poorer telescope for a novice, but the story illustrates the "aperture fever" that is rampant in our hobby.
A friend purchased, after listening to the advice of supposedly knowledgeable amateur astronomers, a 10" aperture Newtonian, also on a Dobsonian mount. That scope got used about three times before the owner realized that he was spending more time assembling and collimating his scope than observing with it. He soon switched to a 90mm APO refractor and has never looked back. He later told us, "No one told me that the 10" Dob was a pain in the knees, back, neck and patience; it gave brighter, blurrier images than the 90mm APO."
The point of these sad stories is that telescopes can just as easily be too big as too small. A subtext is that quality, both optical and mechanical, is more important than quantity (raw aperture). A good quality scope of moderate size will usually reveal more detail about the wonders of the universe than a big, crude scope.
Try to learn at least something of the night sky with your very first telescope, regardless of its inferiority to the scopes the guys in the club own, before you upgrade. You can use practically any telescope, even a terrestrial spotting scope, in conjunction with a star map and a binocular to learn how to star hop. Learn how telescopes, eyepieces and mounts work. Learn how to quickly align an equatorial mount, at least close enough for casual visual observation. (We are doing a brief article about that.) Alignment is not difficult and should not take a lot of time. Achieve this modest level of expertise before you upgrade to an intermediate level telescope, so that you can make an informed decision.
When you decide to upgrade to a "real" telescope, resist the temptation to plunge into an advanced level instrument that is larger, more complicated and more expensive than you really need. For help on choosing a new telescope, see our article "Guide to Beginner, Intermediate, Advanced and Expert Astronomical Telescopes." which can be found on the Astronomy and Photography Online index page.
A good example of an appropriate step up from the usual entry-level telescope is the Celestron Omni XLT line. This is a line of intermediate level telescopes that are reasonably priced, well designed and engineered, well made and supplied with an equally good German EQ mounting system. Sky-Watcher, Orion and Vixen offer equivalent models and mounts that will not break the bank. All Omni XLT telescopes include a manual CG-4 mounting system with precise slow motion controls. Omni XLT telescopes include 4" achromatic and ED refractors, a 5" Schmidt-Cassegrain (SCT) and a 6" Newtonian. Any of these would make good novice/intermediate telescopes.
For the affluent novice, a Stellarvue or Tele Vue APO refractor in the 90mm to 105mm clear aperture range, or a Questar 3.5" Standard Maksutov-Cassegrain would be hard to beat. These scopes are so capable that you may never want, or need, to upgrade again. If you later add a larger scope, you will want to keep the smaller scope and if you don't, you will be sorry.
The upper limit in aperture and physical size that most novice astronomers should consider is a high quality 6"-7" catadioptric (CAT), 6" Newtonian reflector or 4.5"-5" APO refractor. These are very capable telescopes, many of which are considered advanced level instruments. They will often out perform larger telescopes in the field. The Celestron C6 (a 6" aperture, 1500mm focal length SCT) might be the ultimate telescope for the serious novice. It is economical, compact, lightweight and very capable. It can be purchased as an optical tube assembly (OTA) and mated with a manual CG-4 mount (also available separately), or bundled with a CG-5 (computerized go-to) equatorial mount. Either way, you have a very flexible telescope system with plenty of room to grow.
The absolute biggest telescope a novice should buy is an 8", f/10 CAT, which is a very powerful instrument. The Celestron C8 has been around for some 50 years and is the most famous of these, although competing models are offered by Vixen and Meade. (There are a couple of C8 reviews on the A&P Online index page.) A C8-XLT is about 10" in diameter, 17" long and weighs 12.5 pounds. This scope requires a substantial German equatorial mount, such as a Celestron CG-5 or Vixen GPD2. These advanced level scopes are probably a little too much for the average novice, unless he or she is already a dedicated observer.
Whether you choose a medium priced model from Celestron, Sky-Watcher, Orion or Vixen, or a high priced model from Stellarvue, Tele Vue or Questar, the telescopes recommended in this article are portable, easy to use and allow the novice to grow in the hobby. In a nutshell, they are the kind of scopes that get used. Many expert astronomers are using the same or similar telescopes. They know scopes that are easy to use get used, while the giant dinosaur-scopes languish in storage.
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