This was a little project we did, looking at a way of getting around uncertainties in measurements of eye position. During vision experiments in the awake monkey, scleral search coils -- hair-thin wires implanted around the animal's eyes -- are used to measure where the animal is looking. This enables you to check that the animals are fixating. However, the animals still make tiny fixational eye movements, which blur receptive field measurements. Some people have also used the coil outputs to correct for these microsaccades, but for this to be valid, the error on the coil outputs would have to be small compared to the scatter in eye position during fixation, and no one had checked that this was really the case. We found that coil measurements were subject to a slow drift. This means that you know where the animal is looking at any given moment only to within 0.1 degree of so, too rough to correct for fixational eye movements. However, because the drift is slow,you have a much more accurate idea of the difference between where the animal is looking now and where he was looking one second ago. We used this fact to do an improved Bayesian estimate of the receptive field profile, removing at least some of the smearing.