Good morning, (I'm not sure if this is the right place for this question.) I want to learn about the Physics of orbits and how to calculate planets' position, velocity, etc. Basically, the only source I have is Internet, but the majority of the sites give incomplete and fragmented information (there is no sequence from basic to advanced and it is not well explained). I have no idea what sequence to follow or even where I should start, because I don't know what is important to know first. My current knowledge comes from high-school Physics and a collection of university introductory-level books (two by Paul Tipler and one from Resnick, Halliday and Krane). I'm still not in college; so, the knowledge from these college books is self-taught. I also have a basic knowledge of calculus, which is also self-taught (from the internet). My question is: how should I proceed? Is my current Physics/math knowledge proper so that I can already look for an introductory book on celestial mechanics? Or is there some other thing I should learn first? Thank you in advance.