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Thinking of checking and collimating my telescope- not much else to do with it living in the North at the moment!


Bearing in mind I’ve never done this before am I better off getting a proper eyepiece instead of trying to make my own? 

It wouldn’t surprise me if it needed doing as the box it came in was quite damaged. 

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A collimation cap is pretty useful for a first check and relatively easy to make. You just need something cylindrical that will fit in the focuser (a 35mm film canister works well if you can find them). The you just drill a small hole bang in the centre, put it in the focuser and look through the hole.  You should be able to see your secondary mirror in the centre of the hole and looking circular, and in the reflection of the primary mirror in the secondary  you should be able to see the donut sticker on the primary forming a concentric ring around the reflection of the peephole you're looking though. 

However I do recommend buying a cheshire eyepiece as they are much more useful and can be had cheaply second hand. 

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I made a collimation cap and added a shiny washer. It makes all the difference and is really easy to use. I tweaked the secondary of my 200P followed by the primary over the weekend and it now spot on.

I am glad I opted for a KISS approach.

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  • 2 weeks later...

You can make a collimation cap using the cap that fits in the eyepiece holder (assuming you have it, I think most scopes come with one).  Measure out where the middle is and drill a 1 or 2mm hole (recommended to use a hobby hand drill, basically a handle for a drill bit, it's very soft plastic).

A Cheshire should help but is not essential, ultimately you'll perform a star test probably outside on a clear night, pick a bright star (Polaris is a popular choice) and defocus until you see concentric fuzzy rings as per your telescope's manual.

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I think the star test is the simplest, easiest and most accurate way to check collimation.
I follow Gary Seronik’s no-tools collimation advice 
https://garyseronik.com/a-beginners-guide-to-collimation and can recommend the Small Optics guide at 

More details:


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Crikey. Been away for a while but decided to see how the scope was today. I wasn’t quite sure what I was looking at in the Cheshire eyepiece but nothing was lined up. So I adjusted the primary to make the cross hairs centralise in the black dot. 

I will see how it goes tonight. First clear skies in weeks up here. Just looked at the moon and it seemed ok - nice and tight focus - even using Barlow and 10mm ep 

I tried following Astro baby guide but found it confusing 🤷‍♂️. When I have more time I’ll give it another go !


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