Saturday, February 22, 2014

pyAstroStack: First alpha release!

First I have to say that this project was a lot bigger than I thought. Even on the limited functionality it has now there was a lot more work I was prepared to. And all that work was surprisingly mostly user interface and saving the temporary files. I'll write a bigger post on all the problems I ran into and let this post be the announcement of the first released version of pyAstroStack.

No, I really haven't come up with a better name...

PyAstroStack 0.1

PyAstroStack is an open source stacking software for astronomical images taken with DSLR. This first version includes basic functionality such as subtracting and dividing images, debayering, registering and stacking. Supported image formats are limited to Canon EOS 1100D CR2 and similar. Don't expect anything spectacular. I'm not very experienced programmer.

Here's an example image what pyAstroStack can do. This is a median stack of about 30 exposures.

Image stacked with pyAstroStack. Full size in


  • Command line user interface
  • CFA to RGB conversion on OpenCL which makes it quite fast
    • Bilinear
    • LaRoche-Prescott
    • Variable Number of Gradients
  • Registering
    • SExtractor and method from
  • Aligning
    • Affine transformations by ImageMagick
  • Stacking
    • Mean value
    • Median value

Supported cameras

  • Canon EOS 1100D
  • Everything else from Canon that has Bayer filter RGGB


  • Command line only. You really need to read the manual to use this. The software could really be user friendlier.
  • There might be a GUI in the future


Download and extract source package. See INSTALL.txt.

Help needed!

I have only access to one camera. Also my data isn't too good, I'm aware of that. That of course limits my test runs. What I would really appreciate is some raw photo sets that allows me to run tests on different features. 
  • Set of some light frames and proper flat frames. I'm bad at taking flats whenever I even bother to take them. This has made it quite difficult to implement flat frame calibrations properly.
  • Single example images from different cameras. This is just to make sure my program recognizes them and is able to debayer them properly. These images don't even have to be astronomical. Just something with recognizable colors.
If you would like to help, please contact via Google+

Wednesday, February 19, 2014

Moon for scale: Part 2

I did some comparison of apparent sizes of deep sky objects and the Moon ( and that seems to be the most visited page on my blog so time for another one. These were actually made the same time with Andromeda and Orion Nebula, but for some reason I didn't include them in that post.

Flame Nebula and Horsehead Nebula

Names for these nebulae are quite describing. Flame nebula is easily visible and Horsehead a bit fainter. That red color is mostly filtered by digital cameras. With a modded camera that has the filter removed all the red details would be a lot brighter. Most people have seen photos of the Horshead nebula, but here's the size illustrated:

Bigger version:


It's not a deep sky object, but interesting whatsoever. With naked eye Jupiter seems just like a star, but even a small telescope or binocular can show that it's not. Here's a composite picture comparing Jupiter and the Moon.

Bigger version:

That's about it...

I don't think I have any more interesting photos to show. There hasn't been too many nights this winter to shoot any astrophotos... Too bad.