Bovy, Lang, and I wrote down a complete model and objective function for our image modeling / astrometric catalog / multiwavelength counterparts project. In principle, the model and objective function is all the science; optimization is
just engineering, but in practice that is never trivial for problems as hard as this one. We also reminded ourselves why the best way to do catalog matching is through synthetic image reconstruction.
Scott Trager (Kapteyn) gave our group meeting talk on stellar populations in old galaxies. When I last worked in this area, the theoretical modeling limited any conclusions. Since then, the already great data have become even better, but Trager surprised me by showing that the models have also enormously improved, in part thanks to him. It might be time to dive back in.