Search the CONFOCAL archive at
http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal

I also suspect that what you see is probably condensation on the 
cooled CCD.  If you want to test for it without opening the camera, 
simply switch the camera off for a day or two and then take pictures 
immediately after switching it on again. If the pattern is gone and 
then returns as the CCD starts to cool you know for sure what you got.

Beat

At 17:29 12-03-2008, you wrote:

>Search the CONFOCAL archive at 
>http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>This is not specifically a confocal question but a microscopy 
>question none the less.  We have a Zeiss axiovert 100M using a 
>Hamamatsu Orca camera.  There seems to be an image artifact 
>somewhere in the optical train.  When I have the live camera feed 
>there are lots of small circles with smaller rings inside.  Could 
>this be dust that has collected somewhere? I have tried cleaning 
>every surface I can get access to but it is still there! I get it 
>whether doing bright field or fluorescence and it is not dirty 
>objective lenses.  It is not filters within the condenser either as 
>the same particles appear in the image irrespective of the condenser 
>position.  I have removed the camera and cleaned it, still no 
>look.  So I'm at a loose end really as to what it can be.  I can 
>only think it is something within the microscope body beneath the 
>objective housing and I don't really want to dismantle the whole 
>thing! Has anyone had similar problems in the past?
>
>Thanks,
>
>Matt Pearson.
>
>
>
>
>--
>Imaging Technician
>Cell Biology Division
>Institute of Ophthalmology
>University College London
>EC1V 9EL
>020 7608 6857
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>