synthetic image modeling

Lang and I discussed once again the issue of matching up datasets at the catalog level, and learning thereby about the positions and motions of stars on the sky. In each of these discussions we always conclude that the limitations of catalog level are such that we always want the images and to work at image level directly. However, today we realized that we could work with synthetic images, created from the catalogs and our model of the sky. The parameters of the model of the sky could be optimized to create synthetic images that best fit the synthetic images created from the set of catalogs. This got us substantially closer to the scalar objective we seek at catalog level.