Hello! I continue to have problems with the images from my SBIG ST402. The dark pixels of the master dark are brighter than the dark pixels in the image resulting in dividing my zero.
At first, I thought it was an issue with how I obtained my darks, resulting in a low level light leak. It has continued despite making sure I have good darks. It occurred with SGPro and NINA.
The guidance at the SBIG forum was that I may have a wrap problem. I’ll try SGPRo with the SBIGDrv.dll 4.9.9.8 (works rather than the latest driver). Someone updated a driver as HomeMade.SBIGDrv.dll, and I’ll try that with NINA after renaming it SBIGUDrv.dll in the NINA file.
I want to get an image with CCDOps; however, the program has decided not to start, so I need to figure that out.
This is similar to the post I started before, “Strange Image After Dark Frame Application,” but since I’m asking if folks have guidance about a possible wrap issue, I thought that I would start a new topic. However, the images in that post also show this problem.
I have attached the image from the run two nights ago from S ORI that shows the problem.
The link to the SBIG forum discussion is ST402 - Strange Image After Dark Frame Application | Diffraction Limited Support Forum
Thank you for your help and best regards.
Mike
S ORI_LIGHT_I_2.00_-9.79_2026-01-07_0000.fits (767.8 KB)
On the SBIG forum, it was suggested that this might reflect electrical interference rather than a wrap problem. Has anyone else experienced electrical interference problems, especially with legacy equipment? How might I evaluate this and what might be the remedies if so? Thanks. Mike
Hello! I’m not sure what to do with this problem. Last night, all images over about 3 hours were affected so that the dark pixels were under the dark pixels of the dark frames, resulting in dividing by zero. Other targets were irregularly affected, though most weren’t
I analyzed the target RR CET by subtracting 400 ADU from the dark frame. This prevented dividing by zero; however, it results in an off set of +100 ADU (native to the camera) for the target and -300 ADU for the dark frame. I don’t know if having different offsets for the target and dark frame would cause a problem. The camera is 16 bit, so the full well is about 65000 ADU. The photometry light curve looks OK when I looked at it.
The camera worked well with 32-bit drivers for focuser and mount and guider, but since I had to go with 64-bit drivers for mount, focuser, and guider when the LX200 mount died, I’ve been having problems.
If anyone can help solve this, I would appreciate it. Otherwise, I might have to donate the camera to someone who has 32-bit equipment since I don’t know how adjusting the dark frame by subtracting a few hundred ADUs affects the photometry. Best regards.
Mike
Looking at your image in SAOimage DS9 and fitswork the only things I see are a small overall ramp and some structure with warm/cold pixels. Pixel level structure like that is often a sign of aging readout electronics. Maybe a power supply problem. The other thing is the difference between a warm and cold pixel is only a few DN.
Diffraction Unlimited forum might be the place to ask…
Jim (DEY)
Thanks! Puzzling, though, why the dark pixels of the image are several hundred ADUs darker than the master dark frame. This also occurs randomly - many images affected while some are not.
Curiously, I had a few images in the run of RR CET where the variable had saturated over 65000 ADU while the neighboring images were about 300000 ADUs.
It has a new power supply, though I can try a different one. No change when I ran without the dew heater going. Perhaps it is just aging electronics! Best regards.
Mike
Hello! The last hardware thing I can think of is to try the regulated power supply that came with the ST402 from SBIG as opposed to the power supply I got from Starfront. I doubt that will do much, but it is worth a try. Best regards.
Mike
The key to debugging is to start at the beginning could be at the sensor and change one thing at a time.
Jim (DEY)
Thanks for your guidance.
Unfortunately, SBIG said that they lack replacement parts, so camera specific issues could only be dealt with by transferring the BVIC filter wheel to a working ST402. That might be a good solution, given the linearity of the camera. With BVIC filters, it is a good photometry camera, even with the 12’x20’ FOV on a SCT with focal reducer.
Mike
Success! The run last night with the new power supply to the SBIG ST402 looked much better. No noisy images that had to be discarded. I’ll test for a few more nights, but looks like the new power supply for the ST402 took care of the problem. Best regards. Mike