Paulpci wrote: If I may ask a rudimentary question: what is the purpose/goal of stacking astrophotography photos? I understand merging exposures for hdr, but what is the deal with stars, the moon, whichever? I would like to find out as my girlfriend loves everything astronomy. Someone else probably can explain much better than I can, but seeing as nobody has responded yet I'll chip in with my understanding. Think of taking a long exposure and breaking it into shorter individual exposures.

I use Helicon Soft Focus for stacking images for 3D image building in medical field, but it's a great photo stacker for general focus work. It's a Mac only astro. Online olm to csv.

How to find a group in excel for mac. If you simply combine the exposures (a simple example of stacking), in principle you should get the long exposure back. The benefit of having individual exposures is that if there is subject movement, then the motion blur is much reduced on each individual exposure vs the full long exposure, and you can try to align the individual images before combining them. In this way, you can get the long exposure needed in astrophotography but reduce or eliminate star trails. Another benefit of stacking is to realize improved resolution through multi-sampling. If you take a photograph of same static image multiple times and average the individual images by stacking, then you get a stronger signal to noise ratio since the different noise between images gets averaged to a lower level while the signal is preserved.

It's possible to pick up additional details this way (I guess it's analogous to using a lower ISO than available on the camera). Paulpci wrote: If I may ask a rudimentary question: what is the purpose/goal of stacking astrophotography photos? I understand merging exposures for hdr, but what is the deal with stars, the moon, whichever? I would like to find out as my girlfriend loves everything astronomy. There are a number of different kinds of astrophotography that benefit from stacking. I will just answer your question in the area I'm most knowledgeable - lunar/planetary imaging.

For that type of imaging, one of the best programs is Registax, but others use Avistack. Registax is free, and I believe Avistack is also. Unfortunately both of these programs are Windows only. So you'll have to use something like Bootcamp or Parallels to run a virtual Windows session.