Hi, I recently got a STX 16803 and now I am trying to set it with Maxim 6.3 version. The camera seems working fine but I have some doubts on the darks and images. The darks show two opposite bands on the edges which are quite brighter than the rest of the image. I dont know if it is normal or if there is something wrong in the camera or maybe there is a light leakage somewhere in the optical train? Or even the shutter that doesn't close completely? Ihope the sensor is not damaged. The cam I checked the drivers and the firmware and they are the most recent ones. In attachment few pictures where you can see the problem. Could you please let me know your opinion? Thank you in advance, Marco
Sorry I made a mistake on one image: the last one, i.e. the NEW DARK -30°C 900s was not in bin1 but in bin4. Please dont consider it. Here the right one where the two bands are still evident but less strong....anyway I am afraid the camera might have some problems. Any help is appreciated. Thank you in advance, Marco
Sounds like you're doing these tests on your desk, since you didn't supply any images of stars. The camera shutter can't completely block daylight conditions if the camera isn't capped, because the camera is so sensitive. Make sure the camera is capped when you do the test. I would also recommend using the SBIGDriverChecker to ensure that you have the very latest firmware and drivers.
Hi Doug, Thank you for your prompt reply. Actually I did the tests with camera mounted on the scope which is in a fixed observatory. I took darks also during the night but the results were similar: maybe there was some lights around from PC or red LEDs....Unfortunately I did not have any chance to take yet a real image with stars till now because I put the camera on the scope just 10 days ago and wheater conditions here have been always bad and the sky always cloudy. As soon as I have few hours of clear sky I will take some images. Meantime, what I can certainly do is to take the camera off from the telescope and cap it and then take some darks to see how they look. That would allow to see if the bands disappear or not. I just checked with the SBIG DriverChecker and here are the actual driver and firmware in my cam: I will update when I will have the new darks with the camera capped. Thank you Marco
Okay that's not a light leak then. The only possible reasons then would be: IR Preflash LEDs not working correctly (there's a failure mode whereby they can glow very faintly when not in use) Slight power supply or clock instability, producing a baseline shift during readout. Personally I'd suspect the latter. In that case, as long as it subtracts out it is not a concern and you can get good images. I'd suggest testing the camera on the sky, with appropriate dark subtraction. If it works well then I would use the camera as-is.
Thank you Doug. I will follow your suggestions and I will get back as soon as I have decent wheather condition to allow test the camera on the sky. have a nice day Marco
Hi Doug, Unfortunately weather conditions are still bad here and I still cannot test the camera on the sky....Hopefully this weekend would be clear sky... Meantime, I was thinking about another possible reason. Maybe I am totally wrong but I will tell you anyway: since the camera is quite hold and it has not been sed for several years, it might be possible that the thermal contact of some edges of the CCD with the heat sink is no longer working well (the thermal conductivity between CCD and heat sink is lower-worst on some edges than in the rest of the CCD) so the cooling of the CCD surface is not homogeneous? I mean maybe in the center is -30°C and at those brighter edges is as for instance -20°C and maybe the noise increases? The previous owner send to me an old dark and it looks much better Thanks
The CCD is mechanically pressed down onto the cooler stack by a spring-loaded assembly that also performs the function of a light shield. So that seems unlikely.
Hi Doug, yesterday finally the sky was clear for a couple of hours and I have been able to run a quick real test on the sky. The sky condition was not terrific but enough for the test. I took an image in bin1 600s -25°C and I fully calibrated it - Bias, Dark, Flat. The calibrated image looks good and quite even. I think the effect on the edges of the darks, as you said, doesn't seem to have any impact on the quality. I guess you agree, I can use it as-is without problems: may main applications are photometry and new variables search. So the One question: in the event that this effect get worst and more severe, if it is due to power supply or clock instability, will there be a chance to fix it? Thank you for the help!
Good to see that it worked as expected. Yes we can likely repair it if this becomes a problem. We do have limited parts remaining for STX; as I recall we're low on digital boards but okay on analog and power supply boards. This doesn't sound like a digital board thing.
