Hi All, I'm trying to track down the cause of a defect that intermittently appears in the upper left corner of my new [2 months old] STT-8300. I have had the camera out imaging twice and both times I see a "glow" in the upper left corner of some of my images. The defect occurs in about 10% to 15% of my images. Although it is most noticeable in the clear and red filtered images, I also see hints of it in the green and blue filtered images. My usual exposure time is 360 seconds. The interesting thing is that I don't see the defect in my 360 second dark frames but the defect does show up in mt 2 second dark frames [used in calibrating my flat field frames]. The first 2 second dark frame does not show the defect but subsequent 2 second darks do appear to contain a small amount of the effect. The defect will occur when the "Vdd Normally Off" setting is checked and when it is unchecked. Hopefully someone here can advise as to a solution. I hate to throw away 10 to 15% of my subexposures. I checked the camera's drivers - they are up to date. One of the two firmware files - sttga.bf2 is version 2.58. I notice that there is a newer file but I haven't updated that firmware file yet. I have uploaded two reduced size image files - glow.jpg and no_glow.jpg - which shows the defect. View attachment 1401 View attachment 1402 View attachment 1401 View attachment 1402 View attachment 1401 View attachment 1402 Thanks in advance for the help. Dean J.