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How to Buy a Telescope Part I: Rules of the Game

July 18, 2014

Credit: Jeff DeTray

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Here is advice on how to buy (or not buy) a telescope. Amateur astronomy is a hobby that can hold your attention for a lifetime, so it’s worth starting out right. 

You don't need to spend a fortune. But whatever your price range, you want to get the most for your money. 

Inexperienced telescope buyers make the same unfortunate mistakes year after year. It is far too easy to spend your hard-earned dollars on poor-quality instruments, and the awful performance of these telescopes often discourages users from pursuing their interest in astronomy. This guide will help you to spend your telescope dollars wisely.

Before we examine the different types of telescopes you might purchase, let’s discuss some ground rules.

The Rules

There are four important rules for buying a telescope.

  1. Learn the sky before you buy.
  2. Have realistic expectations.
  3. Know what to look for (and what to avoid) in a telescope.
  4. Purchase from a knowledgeable vendor.

Let's look at each of these.

Rule 1: Learn the sky before you buy.

Buying a telescope before you know your way around the sky is like buying a car before you know your way around town. Unless you have some idea of where you are going, neither the car nor the telescope can get you there.

Except for the Moon, which is easy to find, the locations of most other night sky objects aren't particularly obvious. In the excitement of using your new telescope, simply pointing it toward a random part of the sky can be interesting ... for a while. However, frustration quickly sets in when you realize that you have no idea how to find the really interesting sights that await you in the night sky.

At the very least, you need to be able to identify the bright stars and major constellations with your unaided eyes. A simple cardboard device called a planisphere, or star wheel, is a good tool with which to begin learning your way around. Planispheres cost between $5 and $20.

If you have a smart phone or tablet, there are planisphere-type apps available for both iPhone/iPad/iPod and Android devices. The better ones use the GPS capability of your device to display the sky as seen from your precise location.
 

A cardboard planisphere or smart device app can help you to learn the sky.

Along with a planisphere or app, you’ll want a good book or two to help you understand what you're seeing. Click here for some recommendations.

An excellent alternative to telescope ownership is a pair of binoculars. Many of us already have binoculars tucked away in a closet, and these are a fine way to increase your enjoyment of the night sky. With binoculars, a whole new level of detail becomes visible. There are entire books devoted to binocular astronomy.

Binoculars have the important advantage of presenting you with a normally oriented view of the sky. In contrast, astronomical telescopes usually present an image that is upside down, mirror reversed, or both. Binoculars are extremely convenient, too: Just grab them and go!



Ordinary binoculars provide good views of the night sky and are easy for beginners to use.

I know that it’s hard to resist the immediate gratification of owning a telescope—it’s especially difficult for kids—but you’ll be much happier in the long run if you learn the sky before you buy. Once you can recognize the constellations and the stars with your naked eyes or binoculars—and you’re yearning for more—that’s the time to step up to a telescope.

Rule 2. Have realistic expectations.

Some people are disappointed by their first views through a typical amateur telescope. Objects appear much smaller than they expect, colors are extremely subtle at best, and the view is usually upside down, mirror reversed, or both! The view never measures up to the spectacular images produced by the Hubble Space Telescope and other spacecraft. We have all been spoiled.

Left: Photo of Saturn from the Hubble Space Telescope. Right: Simulated view of Saturn in a small amateur telescope.

If your expectation is to see colorful and detailed “close-up” views of celestial objects, a nice picture book or astronomy Web site are better options—less expensive than a telescope and useful even on a cloudy night!

For me, the joy of using my own telescope comes not from the quality of the images but from the fact that I am seeing the objects directly, with my own eyes. I’m not looking at a picture someone else has made. I’m not looking at pixels on a computer screen. I am looking in real time at the REAL THING. I’m seeing photons of light that have been traveling across the universe for thousands—or even millions—of years, just waiting for me to point my telescope, capture them, and send them to my own eyes.

Unusual among the sciences, astronomy allows amateur observers to work with the exact same source material as the greatest scientists in all of history. When I observe the rings of Saturn, my eyes are seeing the very same rings that Galileo first saw in 1610. When I point my scope toward the Great Spiral Galaxy in Andromeda, I see the very same galaxy that helped Edwin Hubble determine the scale and structure of our universe.


The good news is that just about any telescope that you purchase will be far better than the one Galileo used to discover the rings of Saturn and the moons of Jupiter.

I’ll never hold the actual Rosetta Stone in my hands or personally unearth the jaw of a T-Rex or trek to India to see an actual Bengal tiger in the wild. But from my backyard on a clear night, I can look at the Moon with my telescope and see its mountains and craters with my own eyes. I can see the polar caps of Mars for myself and not depend on someone else to show me a photo.

This is empowering.

Rule 3: Know what to look for in a telescope.

What’s the most important specification of a telescope? Many people mistakenly believe that magnification or “power” is most important. This is not correct. In fact, magnification is nearly irrelevant when choosing a telescope!
Actually, the main purpose of a telescope is not to magnify, but to gather light. The more light you can gather, the more you will see. The light-gathering ability of a telescope is determined by the diameter of the scope’s main lens or mirror, known as its aperture. All else being equal, the larger the aperture, the better.

Makers of poor-quality telescopes take advantage of the common misunderstanding about “power” by claiming that their telescopes provide absurdly high magnification, such as “525x” or “675x.” This sounds good, but it is a sure sign of a poor-quality telescope—AVOID IT!


 

Outlandish “525x POWER” claim—a sure sign of a poor-quality telescope!

Never, EVER buy a telescope whose main selling point is its “power”!

Besides, you can adjust the magnification of any telescope by using different eyepieces, much like changing lenses on a camera. Any telescope can be made to provide a wide range of magnifications, simply by switching eyepieces.

As a practical matter, very few telescopes—even extremely expensive ones—are capable of providing good, clear images at extremely high power. For general observing, low to moderate power is much more useful than high power. Most observing is done at magnifications of 50x to 150x. Absurd magnifications such as “525x” or “675x” are rarely useful except with the largest, most expensive telescopes in pristine viewing conditions.

Rule 4: Purchase from a knowledgeable vendor.

Department stores, discount stores, online auctions, and TV shopping networks often sell low-quality telescopes at inflated prices. This is where you’ll find outlandish claims about the “power” of their cheaply made telescopes, because high power sounds impressive. But now you know (see Rule 3 above) that “power” is not an important factor in selecting a telescope. And “Good luck!" if you attempt to seek advice or assistance—the places that sell such telescopes generally know little or nothing about them.

The best place to buy a telescope for stargazing is at a dealer that specializes in astronomy. Not only will you get a better value, but also you’ll establish a relationship with a vendor who can provide advice, accessories, and service (should it ever be needed). Dealers are generally quite willing to explain things and recommend a ’scope that is right for you.

Most major cities—and a few smaller ones—have at least one good telescope store. It’s worth seeking them out.

There are also some excellent online telescope stores. Some of their catalogs amount to a mini course in astronomy. Buying from an online dealer may not give you the same personal service that you get from a store, but the best ones do a fine job of customer support.

This is not to say that you’ll never find a good telescope in a discount store or on a TV shopping channel or online auction. Good telescopes are occasionally available from all of them. But you have to know exactly what you’re looking for, and even then, the prices are seldom a bargain.

To learn more about types of telescopes, see "How to Buy a Telescope Part II: Which Telescope is Right for You?"

Clear skies,
Jeff DeTray, Astronomy Boy
 

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