The morning session was about dark energy, with Sawicki (Heidelberg) taking the theory side and various observers taking the data side. Highlights for me were the weak lensing talks, with von der Linden (DARK) talking about measuring cluster masses and Bard (KIPAC) talking about cosmic shear. During Bard's talk I came up with three possible short papers about weak lensing methodologies, which Marshall, Bard, Meyers (KIPAC) and various others refined over lunch:
The first paper obviates all the problems with transferring stellar PSFs to galaxies by measuring the PSF using the galaxies. LSST can do this because it takes many images under different PSFs. The second paper uses the configurational separations of features (think peaks) in galaxy images to measure shear, independently of, or in concert with, ellipticity measurements. In principle this might be useful, because point separations depend only on astrometric calibration, not PSF determination. The third is to use image-to-image variations in astrometric distortions to infer image-to-image changes in the PSF. I think these two things have to be related, no? This latter project has probably already been done; it requires a literature search.
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