Orbital Elements--Identification of method I'm looking at a book that has a method for calculating the six orbital elements. I'm attaching the relevant pages. My knowledge about orbits is limited to knowing the meaning of the six elements. What I'd like to know is where did these equations come from, and is the author right when he says, "e from (87) and (88)" at the bottom of page 39. I suspect he meant 86 and 87. I've heard of Gauss' and LaPlace's methods for determining orbits. Is the approach given one of those? He notes Herget as a source at the top of page 40. I have access to it, but is not a simple matter to browse through to find the approach on page 40.