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I don't have an equatorial mount nor I plan to buy one. However, I would like to stack my night sky photos.

Is there a software that can easily de-rotate my images so I can stack them? By easily I mean something graphical. I have played with Iris but it is quite complicated for beginners.

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The Hugin panorama stitcher can be used to align pictures. The align_image_stack executable is part of Hugin and can be run as a standalone command line program. To align pictures im1.tif im2.tif, im3.tif,..., you can give the command

align_image_stack -a al -C -t 0.3 -c 20 im1.tif im2.tif im2.tif ....

which will output the remapped aligned pictures al0000.tif, al0001.tif, al0002.tif, etc. Here the -a option sets the prefix of the remapped image files, chosen to be "al" in this example, -C means that the output files are all cropped to the same size, "-t 0.3" sets the maximum tolerance for the control points to be 0.3 pixels (the default is 3 which is too large if there are no good reasons why you shouldn't get almost perfect alignment) , "-c 20" sets the maximum number of control points in each 5 by 5 subdivision of pairs of images to be 20, the default value is 8.

If you add "-p test.pto" to the command, then you can open the file test.pto with Hugin and then modify the control points, do the remapping with different option or make other changes.

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  • I have 21 6000x4000 jpeg images and it has been processing for more than an hour. Is that normal? – Frederico Schardong Nov 16 '15 at 23:55
  • @FredericoSchardong An hour is way too long. Removing the -C option so that you don't ask the program to find the optimal cropping may help. Sometimes the algorithm to find the optimal cropping gets stuck. So, I would just add the -p test.pto option and then use Hugin to improve the results. – Count Iblis Nov 17 '15 at 0:00
  • For astrophotography you would be better off shooting RAW and not jpg – James Screech Jul 13 '16 at 11:45

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