Telescope Buying Guide

Telescopes have been around for ages, or rather, centuries. You're looking at one made by Isaac Newton. That's a statue of the great brain, too.
Telescopes have been around for ages, or rather, centuries. You're looking at one made by Isaac Newton. That's a statue of the great brain, too.
Peter Macdiarmid/Getty Images

Picture, if you will, the astronomer: an older, spectacled lady sitting on top of a mountain for years, culminating one day in the extraordinary spotting of a cosmic supernova. Now picture some old fogy in New York City, keeping a judgmental eye on the domestic scene of his neighbors across the street. While only one of these people might be changing the course of science and thus human history, it's not out of the realm of possibility that they're actually using the exact same telescope.

OK, it's kind of unlikely unless that the old guy in New York has a multimillion-dollar telescope. But the truth is, an astronomer can find some astounding sights with some fairly standard equipment. Consider the case of 10-year-old Canadian Kathryn Gray, who discovered a supernova from her own backyard. About 240 million light-years away, Gray's find guaranteed her a place in astronomical history (not to mention an excellent "special skills" section on future resumes) [source: Matas].


But with scopes ranging from $50 for a department store offering to somewhere around $1 billion for the most expensive telescope in the world, you can be forgiven for not knowing where to start when trying to pick out your own scope [source: Satherley]. We'll explore not only the different technology that telescopes use but also which ones might be a good fit for you.

And as technology advances, it's not just spotting cosmic activity that has become easier. With smartphone apps, digital imaging and simple software programs, we'll also give you tips about what accessories you can team with your telescope to capture images and stream video.

So let's turn our eyepieces to the next page to learn a little about the two main types of telescopes you'll find yourself in the market for.


Reflecting, Refracting and Cassegrain Telescopes

Before we get into more of the nitty-gritty of telescope buying, there are a few things you need to know to understand what the heck you're looking for. Telescopes are fairly simple instruments, but they're not one-size-fits-all. In fact, before stepping foot in a store -- or clicking through to a link online -- you should probably have some idea of the two most common scopes for astronomers.

There are two main types of telescopes: refractive and reflective. A refractor uses refraction (how convenient!) to bend light to the optical lens. Refraction is when a curved lens is used to bend light as it passes from the atmosphere to the glass of the telescope lens. The curve of the lens -- and the subsequent bending of the light waves -- ensures that when you look in the eyepiece, the image you're seeing is clear, as the light has been faithfully reflected.


A reflective telescope uses mirrors, not glass lenses, to reflect light. (Remember that what our eyes take in is simply a reflection of light, so the telescope is acting as a "larger," or more magnified, retina.) By using a primary mirror in a reflective scope (or an objective lens in a refractor), you're going to bring a lot of light from a distant object nearer, and clarify (or focus) the image. The eyepiece lens in both a refractor or reflector scope is then going to take that large amount of light and magnify it, so that the tiny, clear image is now a larger, clear image. You can get a good quality reflector scope from reputable brands like Orion for around $120 dollars.

So that's all well and good; a refractor telescope bends light to get us an image close-up and clear, while a reflector uses mirrors to project the image to us. Which one is the one that will let you see footprints on the moon for less than $100?

Fortunately, both refractive and reflective telescopes are extremely useful and can be excellent quality. Unfortunately, they also have very real physical limitations. While a refractor will reflect an extremely good contrast because there's no obstruction between the objective lens and the eyepiece, you can also see a chromatic aberration in the image sometimes, meaning the colors appear a bit fuzzy at the edges.

And while refractive scopes offer great images, their lenses are nearly 10 times as expensive as an equivalent reflective mirror [source: Bakich]. That can make the telescope themselves quite a bit more expensive than reflective, in general, but keep in mind that brands like Celestron offer introductory refractory scopes for around $100. Because of the secondary mirror in reflective scopes, there is some loss of contrast, and there can also be a fuzziness around the edges of the field of view.

Now let's scan the horizon for some more concrete things to look for when buying your telescope.


Telescope Buying Tips

The Celestron 21024 FirstScope Telescope, a simple reflector scope priced at about $30 on Amazon, is one of many telescopes geared at newbie astronomers.
The Celestron 21024 FirstScope Telescope, a simple reflector scope priced at about $30 on Amazon, is one of many telescopes geared at newbie astronomers.
Image courtesy Amazon

When buying a telescope, you'll find amateurs, experts and those who once took an astronomy class in college happy to share a bewildering amount of information. Before getting bogged down with opinions, think carefully about what you plan on using the telescope for. Much like picking out a bike, you can't just ask for a pink, sparkly one; you must take into account what you plan on using it for.

Many serious hobbyists will tell you that the first thing you do is walk right by the department store telescopes. They even have a nickname -- "Christmas junk" -- in astronomical circles, due to their reputation for shoddiness. Many of them offer extremely high magnification as an enticement, but you can easily increase magnification by changing the eyepiece, so don't be tempted by claims of 800 times magnification for a hundred-dollar scope.


Instead, do look online for reputable dealers recommended by Astronomy Magazine or Sky and Telescope magazine. Beyond that, ring up your local astronomy club and attend a session. The members will have a variety of different scopes and will be happy to let you have a look (along with some good advice, no doubt).

In terms of looking for magnification, remember that higher isn't better. Too high and you're blowing up what you're seeing to the point of losing clarity. To make sure you're not being had, you can calculate the maximum useful magnification of a telescope by multiplying the size of the lens or mirror by 50 (that is, a telescope with a lens measuring 8 inches, or 20 centimeters, across should have a maximum magnification of 400 to work optimally). Greg Scheiderer, editor of, recommends buying several different eyepieces with different magnifications anyway, to experiment with when viewing.

In terms of type, a refractor or reflector telescope -- or one that uses dual technology, called a compound or catadioptric telescope -- are all fine. Although refractors are generally more expensive, reflectors have equally good quality. If you're buying for a kid with a nascent interest, keep in mind that a scope with a 4-inch (10-centimeter) lens might be just fine to start out with; if you've got a more serious hobbyist on your hands, best to stick with something between 6 and 10 inches (15 and 25 centimeters). And remember, the bigger the telescope the more difficulty you might have working with it.

"The best telescope is the one you'll use," as Greg Scheiderer points out. With mounts, photography options and even smartphone apps adding to the stargazing experience, let's zoom in on the next page to pinpoint what kind of telescope -- and accessories -- might be right for you.


Scope Out the Extras

Illustrated here are some of the different mounts you might consider buying along with your telescope purchase.
Illustrated here are some of the different mounts you might consider buying along with your telescope purchase.

So it seems easy enough; you see a pretty scope, take it home, lift it to the skies and voila; you're Galileo reincarnated. In reality, buying a telescope doesn't always mean just buying a telescope.

First of all, you need to consider mounts. Although it might just seem like a handy place to store a telescope, a mount is of paramount importance. An alt-azimuth let's you move the scope up and down (altitude) and left and right (azimuth), and is a simple mount for a scope (about $60-$300). The Dobsonian mount is an alt-azimuth mount with a fixed base. Because it can be disassembled, the Dobsonian is easy to carry from, say, the basement to the backyard.


But mounts can get downright fancy. An equatorial mount has a small motor that moves the mount with the alignment of the stars, while a go-to mount actually has software in it that can locate celestial objects for you. No more guessing between the Big and Little Dipper; simply type in what you want and the go-to mount will move itself and slowly track with whatever you're looking at. A beginning model can run about $300, but some of the best ones are easily more than $1,000.

The reasons people choose to stargaze will certainly affect what kind of telescope you should purchase. Greg Scheiderer, editor of, says that a joke in the astronomy community is that your first telescope should be binoculars. And before you go out and spend thousands on a telescope, do consider that a standard pair of 6 to 10 times magnification binoculars can allow you to see many astronomical activities. (Scheiderer also points out that a good pair of binoculars is a useful tool in establishing a field of view even with a telescope.)

Leaps in technology have made photographing space -- or astroimaging -- a much more accessible hobby. While it's possible to take pictures on film, the advent of digital photography has made astrophotography downright simple. Orion even offers a $60 photo adapter for an iPhone. Simply mount the phone to the eyepiece, find the magnified image on the screen and click for a pic. You can also buy a fairly inexpensive adapter to attach any digital camera (starting at about $30) or a special eyepiece that can capture images on your computer (starting at $60).

It doesn't stop there. For about a hundred dollars, you can buy a bundle of equipment (including USB cable, video eyepiece and software) that allows you to view your telescope's images on your television, laptop or stream online.

And if that isn't enough for you, train your lens on the next page to learn lots more information about how to buy telescopes.

Learn more about telescopes in "50 Targets for the Mid-Sized Telescope" by John A Read. HowStuffWorks picks related titles based on books we think you'll like. Should you choose to buy one, we'll receive a portion of the sale.


Lots More Information

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More Great Links

  • Amateur Astronomer's Notebook. "Excellent 'First' Telescopes." Nov. 13, 2011. (Nov. 17, 2011)
  • Astronomy Magazine. "Buying Your First Telescope." 2011. (Nov. 16, 2011)
  • Astronomy Today. "Guide To Buying A Telescope." 2011. (Nov. 16, 2011)
  • Bakich, Michael E. "Buying a Telescope." 2011. (Nov. 17, 2011)
  • Edelman, Michael J. "The Heretic's Guide to Choosing and Buying Your First Telescope." Nov. 4, 2011. (Nov. 16, 2011)
  • Evans, Robert. "Amateur Supernova Hunting." Swinburne University of Technology. Nov. 19, 2007. (Nov. 16, 2011)
  • Prairie Astronomy Club. "Telescope Buying Guide." 2011. (Nov. 16, 2011)
  • Scheiderer, Greg, editor of Personal interview. Nov. 14, 2011.
  • Satherley, Jessica. "To boldly show: World's most expensive telescope takes first pictures of deepest space in quest for more knowledge of outer universe." The Daily Mail. Oct. 4, 2011. (Nov. 16, 2011)