Spoke with Jo Bovy about finding spectral archetypes among the SDSS spectra; Roweis has code to find (an approximation to) the minimal set of archetypes that
represent all of the SDSS spectra, if we give him the graph of which galaxies
represent which others. This set of archetypes would be the ultimate in non-parametric descriptions of spectrum space; far preferable to things like PCA, which assume that the galaxies come from (and fill) a linear subspace; and it would permit new kinds of galaxy modeling and fitting.
At Pizza lunch, Arlin Crotts (Columbia) spoke about lucky imaging they are doing with a small telescope on Kitt Peak. He described a good night in which they could use two percent of the data for a diffraction-limited (or nearly) stacked image. This led to long philosophical discussions with Schiminovich about whether you can or should use all of the data. I took the position—that you might imagine—that each image must contribute information; there is no way that adding in information from a new image could reduce the information; if adding in less-good images is making the stack worse, then those images are being added in wrongly. Of course adding them in rightly might be damned difficult, since it probably involves something akin to deconvolution (or, as the astronomers say,
In the evening, I spoke to the Amateur Astronomers Association of Princeton about Astrometry.net and the future Open-Source Observatory. Extremely enjoyable!