Starguide - A Practical Guide to Astro-Photography

Release notes on PixelMath V1.8: New version of the PixelMath tool (PixelMath module 1.8.0) | PixInsight Forum

Example of a PixelMath adding two images:

Created with the Personal Edition of HelpNDoc: Bring your WinHelp HLP help files into the present with HelpNDoc's easy CHM conversion