I have recently started using an Orion Starshoot G3 monochrome CCD, and have noticed a dark circle on my images. I can remove this successfully by flat fielding, but it is annoying! See attached image of a greyscale Master Flat (created with a light box), which illustrates the problem.
I took apart the image train, and also tried the CCD on another telescope, and after testing all other possibilities, I can confirm that the problem can be isolated to the CCD chip itself (I even cleaned the glass window protecting the CCD interior, to no avail).
Anyone know what could cause this, or seen this before? Is it likely to be a dust mote on the chip itself, or some flaw in the CCD chip itself? Should I contact Orion about this?
Is the G3 sealed?
if not I would clean the sensor if you can- they are quite hardy as long s you don't rub them or scrub them hard!
I had a similar issue with a WHY 8 and after having it cleaned professionally I realised a bit of isopropyl alcohol then a good side ways blast with a hairdryer works as well.
Looks to me like a dust mote or spot on the sensor
Graz
It's very dark, small with sharp edges so likely to be very close to the chip. Most chips are protected by a glass cover. A little Q tip with acetone and one pass will get rid of it no worries.
Thanks Rick, very useful -- according to that calculation it is 1.6 mm from the sensor (if it is a dust mote), so definitely not on the glass cover. I'm still thinking it may be a flaw in the chip itself.
It's probably a dust mote on the glass cover of the sensor itself. I had a couple on the ZWO, needed a loupe to see it as it was so small as to be undetectable with the naked eye. Looks the same as mine did.
Fortunately the ZWO unscrews to give very easy access, just have to be careful not to introduce more dust than you take out !!!
Thanks Rick, very useful -- according to that calculation it is 1.6 mm from the sensor (if it is a dust mote), so definitely not on the glass cover. I'm still thinking it may be a flaw in the chip itself.
Most sensors have a glass cover slip. Sounds like it could be dust on that.
So an update. I took the camera off, gave it a shake (in an attempt to dislodge what I now suspect was a dust mote on the cover of the CMOS sensor), and attached is the result.
