Collimation Circles Application


Collimation Circles application is EAC (Electronically Asisted Collimation) tool to achive perfect telescope collimation.


Proper telescope collimation is essential for getting most of your telescope. Image such as this beautiful andromeda galaxy can be captured only when all optical elements of your telescope are perfectly alligned.


I struggled for a long time with cillimation process. It's not very complicated when you get used to it, but it's hard to get consistant results. I did some research on the internet and I found two applications for electronically asisted collimation that can be very helpful, but none of them had features that I wanted.


My application was inspired by Mire De Collimation program written by Gilbert Grillot and Al's Collimation Aid. Collimation Circles app combines best features of both and add some of my own. Purpose of this program is not to reinvent the wheel, but rather to learn new technologies, become better at colimating my telescope and to learn something new.

For collimation process itself please check this blog post: EAA telescope collimation with Collimation Circles application.


Collimation Circles is open-source application developed with C# .NET 7 and AvaloniaUI Framework using MVVM architecture patern.

Available on many platforms

Application was tested on Windows 11, Ubuntu Linux 22.04, Raspberry PI OS and macOS 12.

Main window

There are two main parts of interface. It is transparent so that it can be placed over camera stream from your telescope. Main window can be precisely positioned using arrow keys.

Main window displays graphical objects that we will cal patterns. Currently there are five type of patterns supported circle, screw, clip, spider and bahtinow mask.

After running application you will see main window displaying patterns. In the left side of screen there is control panel where you can control properties of displayed patterns in the main window.

Settings window

Settings window is where you configure list of patterns to help you identifiing different parts of your telescope optical path such as:

  • focuser tube
  • secondary mirror
  • primary mirror
  • primary mirror clips
  • primarry mirror collimation screws
  • secondarry mirror spider holder


Setings window consists of three main parts:

  • list of patterns
  • selected pattern properties
  • global properties


Posibilities are limitles. You can export and import your settings to file, witch can be helpful if you have more than one telescope or you want to have profile for each task. For example, you can have profile for aligning secondary mirror and another one for aligning primary mirror.


Actions of tool bar buttons from the left to right order are:

  • Add: clicking on the arrow opens dripdown menu from where you can select pattern you want to add to your setup
    • Circle
    • Screw
    • Clip
    • Spider
    • Bahtinov mask
  • Resets list of patterns to default configuration
  • Save current configuration profile as a JSON file
  • Load previously saved configuration from JSON file
  • Duplicate selected pattern

List of patterns

On the left there is list of your patterns. Click on the pattern in this list to select it as shown on the image. This will display it's properties.


Each pattern can be hidden and shown again using check box infront of pattern. If you decided that you no longer need particular pattern, you can remove it from the list using trash can button on the right


On the top right corner there are properties of the selected pattern. You can change each property by type in it's value or yust use mouse and buttons.

In main window you will imidiatelly see the change.


Each pattern can be customized by it's properties:

  • color: color of pattern displayed in main window
  • radius: overall size of pattern
  • thickness: thickness of pattern line
  • rotation: rotation of pattern in degrees
  • spacing: space between pattern lines (if applicable)
  • count: number of patterns displayed (for example number of screws, spider vains, clips, etc. if applicable)
  • label: label that is displayed to identify pattern in main window

Global properties effect whole setup displayed in main window. Changing any of this properties will affect whole setup.

In the press

Collimation Circles application got noticed by RASC The Royal Astronomical Society of Canada. Mr. Blake Nancarrow wrote excellent article about Collimation Circles application in August 2023 issue of theirs monthly journal. You can get your copy here or you can read part of article below.

BN Jrasc 2023 Aug
PDF – 582.4 KB 136 downloads

Online discusions

There are some interesting online forums with great discussions of Collimation Circles application. See the following list if you are interested:


Application is open source software and completelly free. you can visit GitHub repository for more information or download it from releases page.

Clear skies!


Rating: 5 stars
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Dave Menzer
3 months ago

Great add to astronomy tools!

I'm trying to follow the DSI collimation for an RC. In that the defocused star images become elipses, and can have the centers offset. I would like to be able to quantify this, but there is no way to make elipses, or offset circle centers from each other, there is only a global x/y offset

3 months ago

Dave, thank you for pointing this out!
I have read this ( article and now I think I understand what are you saying.
Currently there is no way to do this with collimation circles. But, I'll put ellipse pattern in my TODO list.

3 months ago

Hi, I was just looking at Collimation Circles. That's exactly what I need. Unfortunately, this does not work from the Raspi 4. The image with the circles is not transparent. I use the Raspi with Kstars and Ekos for my astrophotography and the tool would be a great addition to calibrate my Newtonians
Greetings Tommes

3 months ago

Yes, that is known issue with Raspberry PI OS. Please see the Known issues on the GitHub page on how to enable transparency.

3 months ago

Sorry it doesen't works

3 months ago

Tommes, can you please visit GitHub issue page and open new issue? So that we can discuss problem there.

4 months ago


Thanks for the great app here. Is it possible to include a UVC USB camera in your app? For an example,

Best Regards.

4 months ago

Thank you very much Tommy! In future versions I will add option to display camera stream in app background. But user will still need to provide stream by himself.

4 months ago

hello i am wondering if suitable for sct scope?

4 months ago

I don't own SCT telescope, but Collimation Circles application should be usable with every type of telescope, that needs collimation. For more information please see the article by Blake Nancarrow here: He used it with SCT.

basiglio ribaudo ettore guido
5 months ago

Good but application not trasparent in my Raspberry os64 bit.

5 months ago

Please see instructions on my GitHub, how to enable transparency on Raspberry Pi OS 64bit.

6 months ago

Brilliant tools thanks. Dumb Q - is there an easy process to be sure you have the screw images matching the tube? (I'm on an RC, so 4 vanes, 3 screws)

6 months ago

@DevonRob Thank you for using Collimaton Circles application! I'm not quite sure if I understand your question. But I'll try to answer it anyway.
Screws helper is intended to help you indentify wich screw have to turn.
To align screws on screen with your telescope, you first open settings by selecting gear button in upper right corner. Than from list on the left side ("Item to costumize") you select screw item and make sure that check box infront it is checked. Then you can use "Item properties" to fine tune your screw size, position and rotation.

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