Kepler instrument

Foreman-Mackey and I looked at the variability of Kepler sources, trying to understand the variability introduced by instrument or detector or full-system sensitivity. There are a lot of effects, and they are oddly repeatable from season to season and from star to star, but with massive exceptions. So we don't really understand it. We briefly got to the point that we thought the variations might be additive, but by the end of the day we were feeling like the dominant effects are multiplicative. We got some very nice and useful feedback about it all from Tom Barclay (Ames) via Twitter (tm) and from Eric Ford (Florida) via email. There are many effects, including stellar abberation, stellar proper motions relative to the detector, both for target stars and for nearby stars, photometric mask issues, and spacecraft thermal and reorientation issues. We need to learn a lot!