I built a free tool to generate Messier & Caldwell catalogs posters - Forums

Topic starter

Sep 11, 2025

Hi everyone,

I started astrophotography a month ago and took the challange to capture all the Messier objects.

I looked out for a nice way to track my progress and have a printable poster when I'm done... Couldn't find any, so I built it!

I wrote a Python script that automatically generates a grid of the Messier (110 objects) or Caldwell (109 objects) catalogs.

Just drop your pictures in a folder, run the script and here’s the result:

📷 Messier Catalog progress (20/110)You can configure a lot of parameters like the size, title, font, number of columns, bigger object’s size and position, etc…

Give it a shot and share your result here! It’s free on my Github account:
https://github.com/sylvainvillet/astro-catalog

Let me know if you have any feedback 🙂

Clear skies! 🌠

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andrea tasselli

Frequent contributor

Sep 11, 2025

Thanks for sharing.

Jim Miller

Sep 11, 2025

This is great. I would like to find a tool with a bit more flexibility, that allows for different numbers of images that may not be associated with Caldwell or Messier. Maybe it already exists.

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Ole Skanning

Sep 14, 2025

Great feature, which I just had to try. However I could only make it work, if I changed the below line from

font: ImageFont.ImageFont | ImageFont.FreeTypeFont,

font: ImageFont.ImageFont, #| ImageFont.FreeTypeFont,

Otherwise I got this error: TypeError: unsupported operand type(s) for |: 'type' and 'type'

Then it worked, at least with the standard parameters.

I am on Mac M3, don’t know if I need to update python3

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Sylvain Villet

Topic starter

Sep 15, 2025

Ole Skanning · Sep 14, 2025, 07:53 PM
unsupported operand type(s) for |: 'type' and 'type'

Hey Ole,

thanks for the report, indeed this operand is only available on Python 3.10+ (released in 2021), so you might want to update 🙂

I updated the README accordingly.

Otherwise I just released a new version 1.1.0, which adds the ability to group objects into the same slot (like M31, M32 and M110)

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CVZ_Astro

Sep 15, 2025

That’s really useful. Thanks Sylvian, I’ll try it!

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Sylvain Villet

Topic starter

Oct 20, 2025

Hey star hunters,

I just released a brand new version of Astro Catalog, now with a nice User Interface instead of the command line script! The image is updated automatically each time you change a setting.

I also added a new Basic layout where all the objects have the same 1x1 size, as well as a global scale setting to adjust the size of the final image!

Let me know what you think!

https://github.com/sylvainvillet/astro-catalog