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A blog about a system to determine terrestrial albedo by earthshine observations. Feasible thanks to sheer determination.

CCD alive after all?

Real World ProblemsPosted by Daddy-o Aug 13, 2012 03:06PM

The image below is taken at the IIWI computer with the CCD camera attached to the board, sitting in a PCI slot on the IIWI. The software used is SOLIS.

This image looks like things we have seen before. The broad stripes are reversed but that may be something in the display software settings. It is a very primitive setup - all I have managed to do is take a picture at some long exposure time. The CCD is still attached to the telescope, I think, so the shutters are closed and what we see is a flat+bias frame. As it was dark in the dome when the image was taken the 'signal' is dark current - not light. The bands are structures in the flat field. The spots are noise. The large spots are possibly CR hits?

I think the image proves that the camera is able to take pictures. The noise may be due to a damaged cooler or - more probably - that the cooler is not switched on (I don't know how to do that) yet.

It is at least an image from the camera - so board and camera must be OKish. Why then are there no images when the camera is attached to the PXI? One answer could be that the PXI was damaged during the MLO power surge. I am leaning towards that theory now.

Added later: Here is an image with cooler ON.

The minimum values is 402 - a bit high, but at least it now looks like a bias frame. I would say that there is nothing wrong with the camera or its board. So the problem must be in the PXI!

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Posted by Daddy-o Aug 13, 2012 03:38PM

Added Later: I have now figured out how to turn the CCD cooler on. The images now look like proper bias frames. At short exposure the level is near what we expect: 402 (a bit high - we are used to 397). The string flat field pattern seen when the system was not cooled are thus due to dark-current, not stray light. Apparentlythe dark current follows the sensitivity pattern of the silicon - therefore we see a flat-field like pattern in hot bias frames.