One of our functional tests of astrometry.net is a run through an immense amount of SDSS data, looking to see what percentage we solve (>99 percent) and what percentage solve as false positives (we have never had one, so <3×10−5). I diagnosed a failure today and found this (small cutout shown below). It is an engineering-grade SDSS image, where the PSF is double-peaked, and different stars have different peaks dominant (some left, some right). Now that's what I call bad data. Can we be blamed for failing to solve that?