In order for your telescope to work to its maximum accuracy and efficiency, you will have to give some attention to its optics. One of the most important steps (if not the most important step) you will have to take is collimating your mirrors. It seems like a complicated, confusing and difficult process from the distance, but once you understand what the purpose of it is, you will have no trouble performing this procedure. Here is a step by step guide to help you through it.

Why Is Collimation Important?

To understand why collimating your telescope is not only important but necessary too, you need to know how its optics work. Reflector telescopes use two mirrors – a primary one that collects light before reflecting and directing it to a focal point; and a secondary mirror that feeds the gathered light to the eyepiece, producing the images you observe.

The problem starts when the components of your optics shift out of alignment, and that is something that is inevitable in reflectors. When this occurs, be it from mishandling your telescope, neglect, overuse or even something as simple as transporting or moving your telescope, the optics will not line up and your observations will become blurry, inaccurate or impossible to fine tune for clarity.

Collimation is the process of resetting your optics (both mirrors and your focuser) so that they are clear, precise and neatly aligned.

Do Refractors Need Collimation?

Refractor telescopes do not use mirrors, they work with two convex lenses. These lenses still have to be properly aligned, for the same reason that reflectors do, but the difference is that lenses are typically set in place by the manufacturers permanently and rarely shift. This does not mean that a refractor will never fall victim to misaligned optics, so you may have to collimate at exceptional times. It is more likely that your refractor will need collimating because of severe mishandling rather than being a normal and expected part of maintenance, as it is with reflectors.

How Often Should You Collimate Your Telescope?

This depends on you and your telescope. There are varying opinions on how regularly reflectors need collimation.

Most astronomers agree that in the case of standard reflectors and larger telescopes you should check or test your collimation every time you use your telescope. This is just routine though and does not suggest that collimation is necessary with every use. Other astronomers go by feeling or observation. Regular maintenance is recommended regardless of collimation, so there are some who choose to collimate routinely, for example, every three or so months.

There are two rules of thumb when it comes to collimation, though.

The first is that if you ever move or transport your telescope – especially if you have traveled far or along particularly bumpy roads – you should collimate. Motion is no good for your telescope’s optics and it is highly likely that they will shift position after a journey. By the same token, if you ever bump, or worse – drop, your telescope, you will have to collimate to make sure that your device is not damaged.

The other rule is to go by what you see. If you can tell that there is something off with your telescope’s picture – say it is stopped focusing as it used to, it’s picture is blurry, or there are other distortions in the image – it is a clear cue to collimate.

How to Tell if Your Telescope Needs Collimation

Sometimes distortions in viewing are not a problem with the telescope’s hardware. Atmospheric fluctuations, like temperature, can cause stars to twinkle, and your telescope may produce blurry or unfocused images because of this. There is a simple way to test whether or not maintenance is necessary if you notice that your telescope is not focusing but you are unsure if its due to conditions or collimation.

It is called the star test, and it is quick and easy to do no matter where you are. One opinion is that it is more efficient than using collimation tools, because it pinpoints the problem based on what you use your telescope for, and is therefore more realistic.

How to Collimate a Reflector Telescope

Now that you have determined that there is a problem with the alignment of your optics, you will have to correct it. It seems like an intimidating process, but so long as you understand the desired result, you can choose the method that is most convenient for you.

Use a Cheshire Collimator

Cheshire eyepieces (or Cheshire collimators) are thought to be the best way to collimate a telescope. The tool itself is a peephole that you insert into your focuser, rather than an eyepiece. Cheshire collimators do not contain lenses or mirrors but have crosshairs in place. When light falls on the black build of the Cheshire tool, your telescope’s mirrors reflect and therefore magnify the crosshairs through the peephole or eyepiece. To use one to collimate a telescope, this is what you have to do:

Use a Collimation Cap

If you are lucky, your telescope will have come with a collimation cap made to fit it. If not, they are affordable and relatively easy to find and make a big difference in collimating your gear.

Use a Laser Collimator

Laser collimators are handheld tools that you can attach to your telescope to perfectly center your device’s optics. They are highly effective but can be somewhat tricky to put into practice, as even the slightest wobble can cancel out your collimation. Still, they are handy and well worth the effort. You may just need a little bit of practice.

How to Collimate Without Tools

Though using tools makes collimation all the more easy, it can be done without them. Note that there are a few cons to this, such as a higher risk of inaccuracy in your guesswork, as well as the need to look at stars which might be obscured or distorted by the same atmospheric factors mentioned earlier. That said, this is a great way to touch up your collimation, or for emergency collimation if you are out in the field and do not have access to your tools.

How to Collimate a Schmidt-Cassegrain Telescope

The above methods are for reflector telescopes because they are not built for the easiest collimation. In the case of Schmidt-Cassegrain models, all the collimation tools you will need will come built-in to the telescope. Still, there is a trick to it.

How to Collimate a Refractor

Finally, although refractors should just about never need collimation you might find yourself having to correct the alignment of the lenses in rare circumstances. Honestly, it might be simpler to take it to a professional, as unlike the methods for Schmidt-Cassegrains and Newtonians, collimating a refractor is quite a complicated process. For this reason, if you ever find that your refractor must be collimated, I strongly recommend taking it to a professional rather than attempting it yourself, but here are some general instructions for the sake of knowing.

Conclusion

Telescope collimation is a necessary (if not slightly tedious) procedure that will improve your stargazing significantly. The important thing to remember is that no two telescopes are the same so you will have to collimate yours according to its type, optics, and even model.

Some telescopes come with collimating caps to make your job easier, while some, like the Schmidt-Cassegrain variety do not require tools at all. Refractors are typically the most difficult to accurately collimate, but to compensate for this they rarely need collimation.

In any case, if you do not trust your own ability, or do not feel like doing it yourself, you can take your telescope in for tuning, repairs, and alignment. Just keep in mind that Newtonians/ Dobsonians require frequent collimation, so it is more efficient to learn how to do it yourself.

There are tools available to help you out, like Cheshire collimators, laser collimators, and the aforementioned collimation caps. If you are willing to put some extra time into it, you could always collimate without spending extra on these tools.

Ultimately, it does not matter how you choose to collimate your telescope, so long as you do. It is essential maintenance that will remove interferences, distortions, and inaccuracies from your observations.