Your Telescope Can't See It Till You Find It

Aside from a a stable, well-made, the most important part of your telescope is the finder. You need the mount to hold your scope on what you see, and you need the finder to get it there in the first place. Even a set of so-so optics won't be as damaging to your viewing experience as a problem with either the mount or finder.

Finding the Right Finder

One thing to watch out for in a finder is finders that are made to look good, without actually being good. My favorite finders to hate are the little telescope-looking things on the side of the scope with a cheesy little ring-mount with three screws.

Reflex Sights: Red Dots and Red Rings

For most users, I recommend a Telrad or a similar red-dot/red-ring finder. It doesn't magnify or vignette your view of the sky, so finding things in the sky with it is very natural and easy to do at any skill level. My personal preference is the ones that show rings rather than just a dot, but I have and use both kinds. The way these sorts of finder work is that you look through them and they appear to project an aiming point on the sky. What you look through is a clear piece of plexiglas, rather than en eyepiece like a telescope. This makes it easier to keep your eye relaxed and focus your attention on what you're looking at, rather than the finder itself.

You still have your peripheral vision with these finders, and the view is right-side-up. If you can see the object, you can aim directly at it. If not, you can use a nearby visible star to guide you. For example, the Ring Nebula lies almost perfectly in the middle of two bright stars in the constellation Lyra. If you point your finder at that point, then look through the telescope, you'll see it, even though you can't see it by eye.

This is where finders that project rings rather than dots excel. With rings, you can move a certain distance away from a visible object in the sky to see things in the telescope that aren't visible by eye.

Magnifying Finders

It's possible to locate many objects that aren't visible by eye using a red dot or red ring finder as described above. But it's also possible to find these objects using a good telescopic finder. A good telescopic finder differs from the cheap ones I've warned you away from in two ways:

• It is larger, so it has a useful light-gathering ability.


• It has a mount that securely holds it in line with the main telescope.

The useless models of telescopic finder included with many telescopes look like tiny little telescopes on the side of the main telescope. They are only about 1/2 inch to 3/4 inch in diameter (12mm to 20mm). They are held on a single metal stalk on the side of the main telescope. They don't collect enough light to show you things you can't see with your eyes well, they have a very narrow field of view, and it's hard to align them with the main telescope but very easy to knock them out of alignment.

• If the finder isn't aligned with the main telescope, it's useless.


• If the finder shows too small an area of sky, you can't get your bearings and find what you're looking for.


• If the finder doesn't collect enough light, you can't see the objects in the sky with enough detail to make them out.

To be useful, a telescope-type finder scope needs to have:

• At least 2 inches (50mm) diameter aperture (width across the front lens that lets in light.)


• A mount that supports the finder at two points along its length.

It's also nice to have a right-angle eyepiece adapter to make it more comfortable to use, so that you don't have to crane your neck to see through it.

The better finders are like looking through a one-eyed binocular. They show a wide field of view, they have a good light collecting area, they're rugged and solid on the telescope so that you don't have to worry about knocking them out of alignment. They are also easy to adjust to line up with the main telescope, and will stay in place once aligned for a long time and a lot of moves in and out of the house without adjustment. I have one friend who takes his scope in his car to various observing sites and almost never has to adjust his finder scope.

Use One or Both

Many amateur astronomers use both types of finder, each has strengths and weaknesses. They'll use the red dot or red ring finder to get close to what they're looking for, then use the telescopic finder to home in on their object before looking through the main scope. this works best with especially large scopes, with can show very faint objects that would be harder to locate with the red dot finder alone.

For most new amateurs, the red dot or red ring finder will be perfectly adequate by itself. It will be the easiest to learn to use. I have two telescopes on which the Telrad is the only finder, myself. If you see me at a star party, that's what I'll be using to find my way around.

All I Want for Christmas is...a Telescope That Works

It's the holiday season. Prime time to buy a telescope, either for yourself or someone else. Unfortunately, it's also pitfall season for those getting a telescope for the first time.

Buying for a Youth

You know an intelligent, inquisitive young person. You want to give them a gift that encourages their interest in science, gives them access to the universe for their own study, and gives them a chance to stretch their mind. A telescope is a great choice. Iin astronomy, amateurs are as active in doing real science as the professionals. They may not have first hand access to new data from the Hubble Space Telescope, but there's a whole universe of stuff that pro scopes like the Hubble don't have the time to look at--that's where the amateur astronomers come in.

That first scope can be a blessing--or a disaster. A good scope, even of the most modest type, can be used to learn and grow and do real science. A bad scope can bury an interest in science and convince the poor youngster that they're "no good" at it.

Here are some prior articles I've written that apply to telescopes given as gifts:

If you read no other article, please read
Department Store Garbage Scopes.

Also, at least scan Telescope Mounts, What Not to Buy. It gives some common bad designs to avoid.

You'll also want to know about advertising claims that are misleading. High Magnification: Forget It!" explains why those claims are bogus, and what you should look for (telescopes don't work like microscopes, but advertisers take advantage of people who don't realize this.)

Glance over A Kids' Telescope, if you can.

You may also consider giving a pair of binoculars that are good for astronomy, rather than a telescope. Have a look at Starting Small.

Buying for Yourself

If you're buying for your own use, you'll want to have a look at the above, plus review the articles below:

First Telescope Economics

Don't Buy a Telescope That Doesn't Fit

Want to Test-Drive a Telescope?

Happy Holidays, and may all your astronomy purchases bring happiness and enlightenment.