PSF modeling

Nikhil Padmanabhan and Doug Finkbeiner came to NYU today to talk about astrometry and large data management (for SDSS and Pan-STARRS). We ended up spending most of our time on variable PSF fitting; Fink has a new method that is simultaneously simple, fast, and capable of catching subtle and detailed effects. One of the issues for a future psf.net is the automatic selection of stars apart from galaxies. That's not trivial.