telescope collimation

Why Do Telescopes Need To Be Collimated?

Backyard astronomy is a popular pastime across the world. Lots of people aim their own telescopes at the heavenly bodies on clear nights. They observe the stars, the planets, the moon, and the occasional meteor shower. If you would like to join their ranks, then simply get your own scope or borrow one from a friend. Just be sure to check the condition of the unit before using it extensively. Does it have any physical damage? Are the lenses intact? When you use a good telescope, can you see your targets clearly? If the image is blurry no matter what you do, then you might need to do some collimation.

What is Collimation?

Collimation is the process of aligning the telescope’s optical components to achieve the clearest image. With good alignment, it will be possible for the light to travel in straight lines and get the best focus. If the moon’s craters appear washed out, then collimate your scope to see whether this fixes the problem. You can also do this if you can’t make out Saturn’s rings or Jupiter’s belts. Assuming your equipment has enough power to see these details, perhaps you are dealing with an alignment issue with the lenses and mirrors.

Some types of telescopes are more prone to misalignment than others. For example, reflector telescopes may need collimation every time you move it to a different location. Some people check for alignment every time they use their scope just to be sure. As for refractor telescopes, the optical components are usually set and won’t move much throughout their lifetimes. Their designs are also simpler such that you can count on their stability. Exceptions include accidental drops and mishandling during transport. When this happens, it might be best to contact the manufacturer for support.

Is Collimation Only for Old Telescopes?

The optics are carefully tuned at the factories. You can expect brand new telescopes to come with perfectly aligned mirrors and lenses so you won’t have to do anything special right out of the box. They should work as intended. However, they are likely to move around quite a bit throughout the years as owners take them to different places for viewing. Even the shift from storage to usage and involve enough movement to mess with the alignment, hence the need for adjustments. New telescopes should not provide blurry images but they may do so if they have poor packaging or if they had careless carriers.

Does this Require Professional Help?

For those who are new to the use of telescopes, collimation may seem like a mysterious process that require great knowledge and skill. Reading about it can certainly be intimidating as the instructions may contain jargon that only experienced people can understand. However, the reality is that collimation is a fairly quick and easy process. It should not take more than a few minutes for a typical reflector telescope. You do not need to get professional help just to align your optics, although you can certainly get help if you feel like you need it.

When is Collimation Necessary?

Collimation is not always needed. You can test your telescope to check whether it requires adjustment or not. Some tests will also allow you to spot other possible issues right away. On a clear night, go outside and bring your scope with you. Look for a bright star and put it at the center of the field of view. Some might be tempted to do this indoors and simply open a window. However, it is important to do it outside where the equipment can be fully exposed to the cold temperature. Give things time to settle down before starting the process.

Go back to the star and defocus the image until the blur turns into a disc of light. There should also be a shadow cast by the secondary mirror. In an ideal scenario, this shadow should be right smack at the center since the light source — the bright star — is also at the center. If this shadow is off to one side, then there is a problem with alignment. In the most advanced cases, the blurred disc may even take on a crescent shape instead of a circle which indicates a worse issue. Now that you have check the status of your telescope, start planning its collimation.

How Can You Do Collimation?

Now that we have answered why do telescopes need to be collimated, we move on to the actual procedure. You need to work your way across the telescope starting from the eyepiece, moving to the secondary mirror, and finally going down to the main mirror. These are the only three things that you need to be concerned about right now. Some do this during the day after they have tested everything with the blurred bright star. They like having adequate ambient light to be able to see what’s inside the scope and make the correct adjustments. Others do it during the night so they can check the image right away for any improvements.

The secondary mirror is the small flat mirror at the front that that is held in place by frames called the spider. This mount has adjustment screws that you can play with until you get the alignment right. Be sure to do this slowly and carefully because the equipment is highly sensitive. Don’t touch the mirror directly as you might get oil smudges or scratches on the surface. These are difficult to fix once they are there so you might end up buying replacements. Focus on the adjustment screws to push or pull the mirror so that you can direct light where it should go. Note the changes you made so that you can undo them if things get worse and try again.

Think of collimation as a part of regular maintenance work. If you want your telescope to be at its best at all times, then you need to take care of it and perform tune-ups regularly. Remember that your primary mirror will have its own focal plane where it produces the sharpest images. You need to get everything aligned to achieve this optimum result from your equipment.

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