We know what it’s like when you’ve got a new set-up, and you may need to collimate it. Collimation is essential for any telescope to achieve the best results. In this article, we detail how to collimate a telescope.
Of course, collimation is more important for Newtonian and Schmidt-Cassegrain telescopes, as they are likely to lose it due to their moving parts.
However, you’ll be pleased to know that collimation isn’t difficult. So long as you know how to assemble your telescope, collimating it will be a walk in the park.
We’ll look at the different methods to collimate a Newtonian telescope and how to collimate a Schmidt-Cassegrain.
How To Collimate A Newtonian Telescope
Newtonians are the type of telescope that will need collimation the most. Each time you use it, you should check if it needs collimating, as it must be adjusted occasionally.
There are three different ways to collimate a Newtonian telescope:
- Use a collimation cap or Cheshire collimator
- Use a laser
- Star test
The first two are the easiest ways to collimate your telescope. However, before you begin the process, ensure the device is aligned with the focuser and that the thumbscrew is tightened sufficiently.
You can check this by pushing the collimator into focus and tightening your thumbscrew. However, this won’t be an issue if you have an adapter or compression ring focuser.
When you collimate your Newtonian, you will adjust your mirrors.
Your primary mirror should always have three collimation bolts on the back. However, most manufacturers have also added three locking screws or bolts, which do hinder the process. You can simply remove these.
By adjusting your collimation screws, you will adjust the tilt and tip of your primary mirror. Your primary will rest on a collection of supports, which will then loosen or tighten when you adjust the collimation.
To adjust loosen only one screw at a time and tighten one other. Loosening two screws before tightening another will make the task more difficult.
The secondary mirror will rarely become misaligned. You only need three or four Allen or Phillips head screws to adjust it.
All you need to do is ensure you don’t loosen your secondary mirror so it becomes loose, or you may damage the primary mirror if it falls. Having the optical tube as horizontal as possible while completing the adjustment is a good idea.
Using A Collimation Cap Or Cheshire
Most collimation caps will come with the majority of reflectors. However, you can easily make your own at home. But if you don’t have one, purchasing a Cheshire is easier to save yourself the hassle.
Using a collimation cap or a Cheshire is easy. First, align your secondary mirror to see your whole primary mirror. Next, you need to align your primary.
You will know that the primary is aligned if the secondary is centered on it. So, if you manage this correctly, the primary should appear in the center of your view.
Using A Laser
If you have a laser, you can speed up the collimator process. They’re simple and easy to use; however, depending on your laser’s cost, you might need to collimate it first.
If you do, assemble a simple V-block and adjust the collimation via Allen screws until your beam stops moving when the laser rotates.
When you need to align your secondary, turn your screws until your laser beam is centered on your primary. Adding a central dot to your primary will make this easier, but it’s unnecessary.
Overall, that is all you need to do, which makes it super easy.
Star Test
While this is a relatively simple tool-free way to collimate, it’s more frustrating if you have a long scope. However, if you want to check out this method, you can always use it to ensure you’ve collimated correctly.
If you’re looking from the northern hemisphere, point your scope to Polaris. Aim for a bright star near the pole if you’re in the southern hemisphere.
You should then switch to a high-power eyepiece and defocus the telescope.
The shadow of your secondary mirror should center on the star’s diffraction rings if your collimation is correct. If it isn’t, you should adjust your collimation bolts until it’s centered.
You may see your star moving out of view, but it will always move toward the direction the mirror has tipped. If you tighten it, it will move that way, and if you loosen your bolt, the star will move away.
Collimating A Schmidt-Cassegrain Telescope
The good news about Schmidt-Cassegrains is that they don’t need to be collimated often, but you should check each session. However, it is a little more tedious than collimating a Newtonian.
You must use the star test because you can’t use a laser or a Cheshire.
All Schmidt-Cassegrains have three collimation screws on the secondary mirror holder. Most of them will use Allen heads.
The good news is that this method is similar to collimating a Newtonian telescope. You just need to make a few adjustments with tools.
If you need to turn a screw, you might only have to turn it ¼. While you could attempt the other methods to collimate a Schmidt-Cassegrain, it will be challenging.
So, we recommend you stick to the star test.
Final Thoughts
We hope that you found this guide to collimating your telescope helpful. While not all telescopes will need collimating, we believe it is better to be prepared if you ever find yourself with a telescope requiring it.
While completing your collimation, it is a good time to check the cleanliness of your mirrors. If you find that they have considerable debris on them, you may want to consider cleaning your mirrors.
If you have any more questions about astronomy and how telescopes work, don’t hesitate to check out our other articles. We can tell you everything you need to know about the subject.
Frequently Asked Questions
Collimating a reflector is easy; once you learn how it will only take a few minutes to collimate it. It is all about the learning process.
When you look through your scope, you’ll want to see a diffraction pattern of concentric circles appearing around your star. So, they should look a little wiggly.
If they’re not concentric, you should collimate your telescope.
Since then, I’ve been an avid stargazer and astronomer, and love nothing more than spending my time charting stars, observing planets, and finding constellations.
This is why I decided to start Telescope Guru. I only wish to share this fun pastime with the world. With this site, I hope to answer all of your questions relating to astronomy, telescopes, and stargazing.
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