New STT-8300 horizontal bands

Discussion in 'STT Series (obsolete)' started by letteri, Jun 20, 2017.

  1. letteri

    letteri Standard User

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    My new STT-8300 is showing significant horizontal banding in some images. I mostly see the problem in images that are binned 3x3, which haven't been a problem as I only use that for syncing.

    But last night it showed up in a 2x2 image.

    Both examples are attached.
     

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  2. Tim

    Tim Staff Member

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    Could you please provide the serial number written on the back of the camera?
     
  3. letteri

    letteri Standard User

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    The serial number is T16040822.
     
  4. Tim

    Tim Staff Member

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    Does the same issue occur using CCDOps?

    Does it occur in every image?

    Does it *only* occur in binned images?

    Was it working previously, then recently the issue started?
     
  5. letteri

    letteri Standard User

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    This is a new STT-8300, and the problem has been there since I received it. It was only showing up on 3x3 images, so I had been ignoring it, since I only use those for syncing. But it showed up for the first time in a 2x2 image, which is why I reported it. So far that has been the only 2x2 image, and it has not occurred in 1x1 images.

    CCDOps does not work for me, which I have also been ignoring, but I will report that in a separate thread.
     
  6. Tim

    Tim Staff Member

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    CCDOps is the native SBIG software, so it is very odd it is not working. What happens when you try to use it?

    How about any other software besides "The Sky X" (from the FITS header), it looks like this is what you used for camera control, have you tested any other software, like MaxIm DL?

    Reviewing the production images from your camera, the issue did not occur during production...so my best guess is either a software issue, or some unknown electronic failure. Testing with other software besides The Sky X should help us narrow down the root cause.
     
  7. letteri

    letteri Standard User

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    I get the same results with Maxim DL. I also tried all of the camera download priority settings, which don't seem to affect anything.

    And I have tried replacing the power supply with the one from my old STT-8300, but that didn't help.

    The bands appear to be aligned with bright stars in the image, as you can see in the attached image 'Multiple bands.fit'. The stars are bright, but not saturated.

    You can also see how the alignment of the bands moves with the position of the bright stars in the two images labeled 'Offset test'.
     

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  8. Tim

    Tim Staff Member

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    it is a strange effect for sure...one of our engineers is investigating and feels it is likely a firmware issue, but they have requested 2 more sample images if you could? They are asking for a sample FITS images of 1x1 and 2x2 binning with a start near or saturated to see how it behaves in those particular cases.
     
  9. Doug

    Doug Staff Member

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    You definitely need the star to be saturated. The same field in 1x1, 2x2, and 3x3 all saturated would be ideal.
     
  10. letteri

    letteri Standard User

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    I did that test last night, but I only did near-saturated as I was trying to match the brightness level. Those images are attached.

    I can try to do the same test with a saturated star possibly tonight.
     

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  11. Doug

    Doug Staff Member

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    Can you reshoot the 1x1 frame, but with the star saturated? I want to fully understand the parameters here.

    Also, while you're at it, I'd be interested in two 2x2 binned shots, with one having the star barely saturated, and one having the star heavily saturated.

    Thanks
     
  12. letteri

    letteri Standard User

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    I am not having any luck tonight getting a reproducible error with 1x1 binning, but I did try the barely saturated idea with 3x3 binning and found something interesting.

    Assuming that the raster is reading out L to R, it looks like it starts writing out corrupt data after it hits a saturated pixel. You can see that in the first attached image, 'Saturated pixel', where it hits a single saturated pixel and writes garbage for the rest of the image.

    The same thing also happens in the second image, 'Saturated scanline', except that on the next line it hits another saturated pixel, at which point it resets itself and starts writing correct data again.

    If I expose the image to the point where there are several contiguous saturated pixels within the star, I can't get the lines to appear.

    I don't know if that makes sense, but it would explain why the tops and bottoms of these bands always appear to align with bright stars in the image.

    Cheers,
    Joe
     

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  13. Doug

    Doug Staff Member

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    Yes I already noticed in your previous images that the shifts in background level were happening right at the saturated point. I was trying to determine if this only happens while binning.

    I'm thinking this is a bug in the auto background offset adjustment algorithm. Our firmware guy is skeptical, but I can't think of any other way this could happen.
     
  14. letteri

    letteri Standard User

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    Auto background adjustment as in auto darks? Or pedestal offset? I don't think I had auto darks enabled for these tests. And I can't disable the pedestal offset. In Maxim DL, the minimum allowable offset is 10.
     
  15. Doug

    Doug Staff Member

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    No I'm talking about internal firmware functions. Can you get it to happen at 1x1 binning?
     
  16. letteri

    letteri Standard User

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    Yes, but I am only seeing the bands at 1x1 binning through the SII filter. They have that same pattern of aligning with saturated pixels.

    In fact, every image taken through the SII filter shows the bands, but I don't see them with any other filters taken at 1x1.
     

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  17. Doug

    Doug Staff Member

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    Okay, so this has nothing to do with binning. It's probably just more likely when binned due to the increased intensity per pixel. Thank you for eliminating that potential factor.

    A quick look at the firmware didn't show any obvious issues. We're going to have to try and reproduce the problem here. I have a technique that involves aiming a telescope at a point source at the far side of the building, but it has to be done at night so it's dark enough to work (at this latitude that's after 9 pm this time of year!). Also we're going into the long weekend... which is all to say this will take a few days.
     
  18. Doug

    Doug Staff Member

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    Actually, it's a very dark cloudy day today, so by turning out the lights and stopping down the telescope I was able to run the test. Here's a crop out of one of the frames:

    CCD Image 29529.jpg

    As you can see there is no baseline shift (measurements on original FITS confirms this). The top "star" is just saturated, and the bottom one is oversaturated. (These are thumbtack holes in aluminum foil, with a desk lap behind.)

    Can you please check that you have the current firmware and drivers installed? Download, install, and run the latest SBIG Driver Checker from ftp://ftp.sbig.com/pub/SetupDriverChecker64.exe

    (I recommend installing the latest driver checker, because it has had a few improvements.)
     
  19. letteri

    letteri Standard User

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    I just downloaded and ran the latest SBIG Driver Checker again (for I think the 3rd time this month), and it looks the same as the last version I installed. I have attached the driver list and version number to verify that they are the latest. (By the way, both before and after the new install, the About dialog has the version as 4.03 Build 4, but in the Windows Control Panel it has the version as 4.0.3.5. )

    In your test image, do you know if you are seeing any single pixels at 65535? In the test images that I sent you, what I saw happening is that a single 65535 pixel would initiate a a bad raster encoding, up until it encountered another 65535 pixel, at which point it would reset. The images I sent you also had saturated stars that were not producing the bad scan lines, but upon inspection it looks like all of those were coming in pairs, which would immediately negate the bad run.

    In other words, you would see something like this if there was separation between the saturated pixels:

    65536|xxxxx|xxxxx|xxxxx|65535

    The bad encoding would even extend across scan lines until it encountered another 65535 pixel, or flood the rest of the raster with bad data if it didn't.

    I am attaching an image that I sent earlier, 'Saturated pixel.Light.L.3x3.03sec.fit', because it shows this pretty well. You can see it in the screenshot from Maxim called 'Saturated scanline crop.PNG'.

    In the same image, you can see saturated pixels that don't produce the bands. But it appears that those come in pairs like 65535|65535. So if there is any bad encoding, it would start/stop on the next pixel.

    From the same image, you can see an example of that in the crop called 'Saturated pixel pair.PNG'.

    I don't know if you can derive from only these examples that all 65535 pixels initiate bad encoding, but it is happening often enough and clearly enough that something is going on.

    Cheers,
    Joe

    SBIG drivers.PNG SBIGDriverChecker64 version.PNG Saturated scanline crop.PNG Saturated pixel pair.PNG
     

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  20. Doug

    Doug Staff Member

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    It was definitely going to 65535, in fact one of the "star" images had a flat top 20 pixels wide.

    It's hard to understand how this could be a hardware fault, given the architecture, but it seems to be happening on your camera and not the one I am testing with.

    It occurs to me I didn't try binning (had lots of saturation). I will try it again with binning.
     

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