I wrote series of articles about advanced newtonian collimation and how it's done with Collimation Circles application.

All three parts are available here:

• saimons-astronomy.webador.com/1769915_ad...e-collimation-part-1
• saimons-astronomy.webador.com/1769983_ad...e-collimation-part-2
• saimons-astronomy.webador.com/1769983_ad...e-collimation-part-3

I hope you will find it usefull.

Thanks for these Simon. A suggestion - instead of removing the primary mirror, would it not be easier to just hide it by putting a paper/card into the OTA?

I did try that method too. For larger telescopes, that would probably be easier, but for smaller ones it's very hard to squize paper inside OTA and keep it steady.
I found that removing primary mirror is by far easiest method for me.

Good point. I now need to find a suitable camera to try out the software. The ASI cameras I have dont seem to be able to focus even with the wide angle lens supplied.

Yeah, for colimation we need simple UVC Web Camera or something simmilar. If you found one to be sutable for use in telescope eyepiece, please let me know.
Curently I'm using my Raspberry Pi HQ camera for the process, but manually adjusting focus is real pain.

Something like this would probably do the job:
bit.ly/444Cwzs or this bit.ly/3U4H8B6

There is a new Raspberry Pi Camera Module 3 available with autofocus and a focus range 5cm to infinite. Should be able to do the job using the python Picamera2 library.

Kurt, I totaly agree with you. Raspberry Pi Camera Module 3 seams to be a great option. But I need something more versatile, USB plug&play. No drivers needed.
That's way I think for this purpose UVC compatible cameras (with autofocus and absolute focus support) are better option. Just need to find a right one

I plan to try out with my humble phone camera and share the screen on the laptop where I can run CC Fingers crossed for this weekend

My first attempt to colimate my telescope was with phone camera too. But I quickly realised, that is impossible to place phone at exact center of focuser tube. That wouldn't be issue if at least you could place phone everytime at exact same spot near the center, but that's is just impossible. At least it was for me. What's the point in collimating telescope if your optical path constantly changes? Sure you can do collimation each time you take phone off and back on, but good luck with that. It will be OK for visual observation, but not for astrophotography.

That's why I'm using Rraspberry Pi camera with special case designed and 3d printed. It can be screwed on top of my focuser. This way optical path stays the same while collimation scope and when I'm doing astrophotography. Even if I take my camera off and put it back on.

I hope my explanation make sense for you, why I think using phone camera is not good idea.

Good point. So I think the most practical & relatively low cost solution is use cameras such as the ZWO ASI224 or ASI120 along with the wide-angle lens thats bundled with them

Yes I think that's the best option. If your ZWO act as standard usb camera, you can activate it's video stream directly from CC application, see version 3.2.0-beta3 here github.com/sajmons/CollimationCircles/releases.
If your camera supports absolute focus, you can control that too from CC (see camera controls button for that). With that you get hassle free colimmation of secondary and primary mirror. All you have to do is to change your camera focus distance from within CC app.

I'm not quite sure if this is working in latest version, but I'm working on it and will be available in final 3.2.0 version.

I will try it out this evening. If your application can support ASCOM, INDI then that should be able to support most of the popular cameras.