Version 1.3.1 adds a new menu to the user interface when editing the "red dots" that Starry Landscape tries to place in the sky. This menu allows the user to choose from many, medium, few and no automatically found dots. By choosing the correct option the user can reduce the time needed to get a good mask for the sky. In general, you want the highest number of dots possible without getting too many dots in the foreground that you have to erase. If your foreground is much brighter than the sky, or if there are very few visible stars in the sky, you are often better off selecting "No dots" and then adding a row of dots above the horizon by hand, or simply selecting "Find Sky" and then painting the mask by hand.
See the video below for some examples.
If you have not already read about dark frames and light frames in version 1.3 you should read this.