*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****

Doug,

Your guess is likely correct. 
I used to have a similar system. It is not hard to take the filter wheel off. You can then check the excitation filters and you will likely see physical damages ('turns') on the filter even  with naked eyes. If budget allows, it might be a good idea to change the light source as well. 

Zhaojie Zhang
Director, Jenkins Microscopy Facility
University of Wyoming

-----Original Message-----
From: Confocal Microscopy List <[log in to unmask]> On Behalf Of Cromey, Douglas W - (dcromey)
Sent: Monday, April 26, 2021 10:48 AM
To: [log in to unmask]
Subject: widefield autofluorescence in unlabeled cells - a filter mystery?

◆ This message was sent from a non-UWYO address. Please exercise caution when clicking links or opening attachments from external sources.


*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****

A colleague asked me to take a look at their widefield microscope. It is an inverted microscope with a 100W Hg source, excitation filter wheel, a couple of choices for dichroics in the microscope filter changer and a filter wheel in front of the camera. They are seeing unlabeled cells fluoresce green (FITC/GFP set) with an otherwise black background where there are no cells. The microscope is approximately 15 years old.

My guess is that the excitation filters have failed (or are failing) after being on the receiving end of a 100W Hg lamp for all this time. Any other thoughts?

Doug

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Douglas W. Cromey, M.S. - Associate Scientific Investigator Dept. of Cellular & Molecular Medicine, University of Arizona Life Sciences North, Room 463
1333 N. Martin Ave, Tucson, AZ  85721 USA

office:  LSN 463        email: [log in to unmask]<mailto:[log in to unmask]>
voice:  520-626-2824       fax:  520-626-2097

UA Microscopy Alliance - http://microscopy.arizona.edu/ A collaborative effort to bring information about shared microscopy facilities to the University of Arizona and the community.