So, you got a telescope for Christmas, or maybe you got one years ago and it’s done nothing but collect dust in a corner ever since. That’s a shame because most telescopes aren’t hard to use. Over the course of the next few weeks, our What’s Up segments will walk you through the steps so that you can take your telescope under the stars and look up.

One of the things beginners struggle with is not seeing the object they’re trying to view in the eyepiece, despite it being centered in the finderscope, so this week I’m going to teach you how to align your finderscope.

The finderscope is a smaller telescope on your main telescope with a wider field of view that helps you locate objects in the night sky. Once you’ve assembled your new telescope, you need to align the finderscope with the main telescope.

But first, let’s talk about the most common types of finderscopes, so you know what kind you have and its advantages and disadvantages.

Finderscopes come in two major types: straight-through and right angle.

The average beginner telescope comes with a very small straight-through finder scope or red dot finder, a type of straight-through finderscope that has a little red dot in the middle of the field of view.

Straight-through finders can be harder to use except at low angles to the horizon because after a while your neck will hurt from straining to look through them. Another disadvantage is the view is reversed left to right compared to your eyes, which may be confusing. One advantage is that the eyepiece of the straight finderscope points in the same direction as the main scope, unlike some of the other styles of finderscopes.

Another common type is the right-angle, correct-image finderscope. As the name suggests, it has an eyepiece that is at a right angle to the finderscope body. This type of finderscope is easier on your body because you usually don’t need to contort yourself to look along the telescope axis. Right angle finderscopes mainly come in one type –  correct image – which means they contain optics to flip the image so that it matches your eye’s view.

You can have either or both of these types of finderscopes installed on your telescope at the same time with a special adapter. Many people do since the two types are good for different things.

There are other types of finderscopes that are more specialized. One of these is the Telrad. A Telrad is a more advanced straight-through finder, with three concentric circles projected on an angled piece of glass. They contain no other optics so they don’t magnify the view, unlike the more common finderscopes, but this is a good thing because it allows you to use both eyes to find fainter stars. The three circles are at 0.5, 2, and 4 degrees, allowing you to use star charts (preferably paper to save your night vision!) to hop from star to star to your deep-sky target. We’ll tell you about star hopping in a future What’s Up.

Now to what you’ve been waiting for: how to align one of these finderscopes with your main telescope and actually find one of those faint fuzzies in the sky!

The main principle of aligning the finderscope is to start by aligning with things that are close to you and repeating the process with things that are further and further away so that objects in the finderscope will be visible through the eyepiece, even at higher magnifications.

The first step is to sight along the telescope at a stationary object, like a tree in the distance, so that the object is roughly in the eyepiece. Finding an object far enough away for this can be a challenge, particularly in suburban environments. Nevertheless, center it in the eyepiece, then look at the finderscope. The finderscope will have two or three adjustment knobs or screws, which may require a screwdriver to be adjusted. Experiment with how the knobs or screws affect the alignment and make adjustments so that the reticle – those lines in your view through the finderscope – is centered on the target in the distance. This is the basic process for aligning the finder scope.

You should repeat this process with something that is farther away; since the finderscope is roughly aligned from the first step, you can align it with the Moon. Center the Moon in the telescope eyepiece and then realign the finderscope so that the center is aimed at the same point on the Moon.

Finally, repeat this process on a star for the most accurate alignment. Once you’ve taken these steps, you’re ready to look at something else in the sky.

So, take that telescope, go outside, and look up.

More Information

QuikFinder (Rigel Systems)

Telrad Sight (Company Seven)