Strange pattern on Tek CCD chip

[Charly Marien]

Hi folks,
some years ago, we had a similar problem with a 1k x 1k Tektronix device, which 
was caused very likely by water droplets on the coating during warm-up phase.
At the places, where the droplets had been, the AR coating was grey and the flatfield
taken with the CCD showed the same pattern. We vakuum-baked the device at +100 deg celsius
for some hours, the spots disappeared and the QE was homogeneous as before.
( Tektronix distributed a NOTE ON CLEANING CCD IMAGERS - 12/91 - at that time, and this procedure
was recommended after cleaning the device with freon degreaser )

Karl-Heinz Marien
MPIA Heidelberg