transparency

I spent some enjoyable time working through Bovy's write-up of his work on the transparency or dust content of galaxy clusters (he is comparing mean spectra of red galaxies behind and not behind clusters taken from Berlind's group catalog in SDSS. As expected, we have very sensitive limits on the dust content of the clusters, and it also appears that we have a positive result. But the big challenge is to compute realistic error bars; most bootstrap or jackknife methods will underestimate them.