This video shows how to blend multiple images of stars together with Starry Landscape Stacker to reduce noise.
Starry Landscape Stacker is for Macs only, but Windows users can use Sequator, which does essentially the same thing. With either program, the most important part of the process is what you do in Lightroom or Camera Raw before blending the images together, and this video covers those steps in detail before showing the steps specific to Starry Landscape Stacker.
Although this video is a few years old, Starry Landscape Stacker hasn’t changed much in that time, and the Lightroom steps that I cover also haven’t changed, so everything in the video still applies (with perhaps a few minor changes).