As an astrophotography newbie I have to give the Siril astronomical image processing software an enormous amount of credit. Not only as a great example of free open source software that offers a genuine alternative to expensive commercial apps, but also for the quality of its documentation.
There's no "just ask questions on our Discord server instead" here! There is comprehensive written documentation online and it goes well beyond listing each function, it goes into detail of when and why to use them, how they work, and how to get the best results. And, if that's still not enough, you can buy the book! The lead developer has produced a 200 page A4 lavishly illustrated glossy guide book.
My copy arrived today, and I plan to pass the time waiting for clear skies by reading it.
