Working on the chapters on counterfactual conditionals for the Open Logic Project, I needed some illustrations for David Lewis’s sphere models, which he jokingly called “Ptolemaic astronomy.” Since Franz Berto joked that this should just require \usepackage{ptolemaicastronomy}, I wrote some LaTeX macros to make this easier using TikZ. You can download ptolemaicastronomy.sty (it should work independently of OLP); examples are in the OLP chapter on minimal change semantics (PDF, source).

(This will probably interest a total of two people other than me so I didn’t spend much time documenting it, but if you want to use it and need help just comment here.)

Update: it’s now in its own github repository and properly documented.