[pmrid (Peter)]

Here's something I haven't seen before and can't readily explain.

I did a swap of cameras yesterday and was in the early stages of an image run last night when I noticed this pattern of large squares - a regular grid of 4 rows and 4 columns - 16 squares in all - the whole image - delineated by faint white lines. Not an optical artifact.

It was warm- about 23C at the time. And these CCD's dont have a very powerful cooling system - in fact it's pretty poor. Even with the little bolt-on supplementary cooler SX provide it only manages to get down 37-38C below delta - at best. So last night it was running flat out and not getting below 13.5C. But those are hardly what you might call extreme conditions.

I wonder if anyone has encountered anything similar?

Peter