I have set the masks (and reloaded the config files) for the ITMX spool, ITMY spool, ETMX and ETMY cameras.  Note that these are not the cameras that are used during initial alignment. 

The idea is that with an appropriately set mask to exclude extraneous light on the cameras, we can use the centroid tracking to monitor the spot positions on the test masses over long periods.  These cameras are saturating over the whole central region when the arms are on resonance, so the centering calculation won't be perfect, but hopefully it'll still give us an idea of what is going on. 

None of these had previously had a mask defined. Finding snapshots to help set the mask center and radius was what set off the confusion and investigation earlier.  Elli's script was immensely useful in plotting the images for setting the mask.

Plots below are snapshots from 28 July 2015, around 10:00utc when the IFO was locked.  Overlaid are circles (even though they look like ovals because of the non-square grid) that are equivalent to the masks that I've chosen.  We will see images from inside the circle, and exclude the portions of the image outside the circle.

The centroid values are already trended as slow channels, so we can start looking at the history tonight, particularly if we re-do some thermal tuning tests.