Registax

RegiStax is image processing software for amateur astrophotographers, released as freeware, designed to run under Windows,[1][2][3][unreliable source?

The process relies on the subject (e.g. a planet) being unchanged between photographs, so that any differences can be assumed to be random noise or atmospheric interference.

The stack of images can be in the form of individual consecutive shots or from frames of a movie camera trained on the scene.

[5][6] Cor Berrevoets (Netherlands) began development of the program about 2001,[7] and it was released on 19 May 2002.

[11] To date (September 2022) the latest release is v6.1.0.8 (6 May 2011) which was contributed to by a team of 9 people.

Image of the transit of Venus, shot as consecutive photographs then processed into a single image.
Image of part of the moon, shot as a video then processed into one still image.