I took many pictures of the lunar eclipse from last week with a stationary camera and now I want to merge them so I get something like http://wordlesstech.com/2011/06/26/eclipse-over-the-acropolis/. What is a good (and free) Mac OS X application for doing this?

Can I also get an explanation of how to use the application if its not primarily for that usage?

  • \$\begingroup\$ This may answer your question. Even though it's about sports photography I think the techniques are the same. \$\endgroup\$ Commented Apr 25, 2014 at 1:24
  • \$\begingroup\$ I don't think this is a duplicate of the action shot question, if only because this can be done with a simple technique that does not apply to action shots: because the moon is always brighter than the dark sky, this effect can be simply achieved by stacking all shots with a "brightest" blending (don't remember what it's called in Photoshop off the top of my head, but basically the final value is the max of any of the layer values.) \$\endgroup\$
    – Gene
    Commented Apr 30, 2018 at 21:15

1 Answer 1


This isn't really "stacking" as the term is commonly used. With exposure stacking, all the member images are aligned together, and then mathematically combined to decrease noise, and increase resolution or brightness of specific objects. In focus stacking, the in-focus parts are combined from the member images to get the entire subject into focus.

What you want to do is just to combine a number of images so that the main subject movement shows with a stroboscopic-like effect.

I'd suggest using the Gimp and compositing the images with layer masks to bring in just the moon from each shot. The Gimp is an open source analog to Photoshop, and its usage is very very broad and deep, and there's no easy way to encompass a description of everything it can do easily.

The other tool you may want to consider is Hugin. Hugin is primarily used as a panorama stitcher, to combine images, but if you load up all your member images, align them, and use the masking feature to make sure the moon is included from each shot, and then "stitch", you should get a "clone" shot that includes all the moon positions.

  • \$\begingroup\$ Will this also create light trails from the stars? \$\endgroup\$
    – traisjames
    Commented Apr 25, 2014 at 15:21
  • \$\begingroup\$ No. Stacking software will do that. :) As I said, this isn't really stacking in the conventional sense. \$\endgroup\$
    – inkista
    Commented Apr 25, 2014 at 18:55

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