blind astrometry failure rate

I worked out the (theoretical) blind astrometry failure rate as a function of field size, standard-star density, and angular scale of our quad indexing (remember that?). The failure rate is a very strong function of all variables, for the main reason that we depend on quadrangles of stars, and their abundance goes as the fourth power of number density, fourth power of field size, and sixth power of index angular scale. My calculation is crude, because it assumes all data are good, but it won't be off by many orders of magnitude.