A few years ago, I started prototyping UFO@home, a visual testimony tool inspired by works of Roger Shepard, Richard Haines and motivated by Pierre Lagrange with the aim of improving UFO reporting. As I explained in another post, the benefit of such a tool was also, to me, to allow simulating known phenomena hypothesis (astronomical, balloons, meteors, planes, birds…) in order to validate or exclude them, along with agreement of the witness. Once the prototype done, I needed to produce the most realistic sky rendering as possible. This required re-writing (then, later, extend with ufology features) the state-of-the-art planetarium software, known as Stellarium. Then Stellarium for Java (S4J) was born.