New STT-8300 Image Defect Problems Continue - amp glow?

Discussion in 'STT Series (retired)' started by Dean J., Apr 3, 2016.

  1. Samuel Lising

    Samuel Lising Cyanogen Customer

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    Hello.

    I am wondering if there was any resolve to this issue. I have this same issue on my STT-8300M. I have noticed it in my images for the last couple of months and I believe I just started getting this issue with the latest firmware update. I've been going though my images and I am noticing it on short exposure images (90 sec). It is not as visible on some images but I would say that 50% of the images it is very noticeable and when I stack the images it is unacceptable.

    I have also noticed that I get a lot of noisy guider images from the built in guider. I would periodically get noisy guide images before (that seem to be related to guide star faded issues that have never been resolved) but a lot less then now. I have noticed that the more noisy guide images I get with an exposure, the more noticeable the glow in the top left corner of the image. It's like there is a flash of light inside the camera that is causing the glow in the top left corner and the noisy guide images.

    Please let me know if this glow in the top left corner has been solved and if so, what is the solution. This thread does not seem to have been concluded.

    Thanks.
    Sam
     
  2. Dean J.

    Dean J. Standard User

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    No Sam, this issue has never been resolved.

    I was out with the camera this weekend for two nights and saw varying degrees of "glow" in the green [5 of 18 exposures] and blue [4 of 18] channels.

    The interesting thing was that I didn't see any image corruption on the first night when I was taking the luminance and red channels - although I have seen the issue on these channels too.

    Why the issue appears on one night not but not the other is certainly a mystery. The camera stayed on the telescope for both nights and was not touched. The second night I was sitting about 30 feet from the telescope in my truck monitoring the subexposures over the network and watched the corrupted images as they came in. So it is nothing I am doing such as shining red lights on the telescope, etc. This happens with the camera on all three of my telescopes.

    The camera did go to SBIG repair but they were not able to replicate the issue.

    The good thing is that the ratio of uncorrupted to corrupted subexposures so far is such that PixInsight's image integration algorithm is apparently able to detect the corrupted area as an anomaly and my master images aren't usually affected... usually. Sometimes I have to throw out the corrupted images though.

    Here are a couple of examples from last weekend.

    Dean J.

    glow1.jpg

    glow2.jpg
     
  3. Samuel Lising

    Samuel Lising Cyanogen Customer

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    Hi Dean.

    Thanks for the quick response. The glow from my camera is in the top left as well but not as pronounced. It is mostly visible when I stack the images because it is happens on more than 50% of the images.

    I went back into my images from January 2017 and noticed that I did not have this problem before that time. I had made a couple of major changes to software at that time. First, I upgraded to Windows 10 and second, I upgraded to ACP 8.1. I'm wondering if this has anything to do with the readout mode of the camera or the USB offset. ACP says it's reading as "Raw" mode but perhaps it needs to be set manually. I read in this forum that re-writing the USB offset might help as well. Also wondering if I updated the firmware at that time (I can't remember exactly but it was around then).

    I'm going to do a bunch of testing this week to see if I can isolate this problem.

    What application are you using to capture? If they weren't able to find a hardware problem it leads men to believe both you and I have some thing that is not set right or needs a reset. Did you always have this problem or is it new.

    I will start a new thread this week if I can not figure it out.

    Thanks.
    Sam
     
  4. Samuel Lising

    Samuel Lising Cyanogen Customer

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    Here are samples of my images with glow (both sides of pier), no-glow (both sides of pier) and stacked. all are calibrated.

    I've got the latest drivers and firmware installed and images are being acquired with Maxim DL 6.13 (with latest patch) through ACP 8.1.

    If anyone at SBIG can chime in on whether there is any solution to this issue that would be great.

    Thanks.
    Sam
     

    Attached Files:

  5. Dean J.

    Dean J. Standard User

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    Yes, that glow looks familiar. I have been dealing with it since the camera was new in December 2015 - January 2016. Probably the last time I upgraded the firmware was last summer-fall.

    I use The Sky X to control the camera on a Windows 7 laptop.

    Noting makes sense as to the cause of the "glow".

    I can take 4 or 5 hours of dark frames here at home with the cooled camera operating on the bench without a single instance of the "glow".

    The image corruption will randomly appear in the field while the camera is imaging an object.

    It will occur in the middle of a series of exposures on a single colored filter so it does not appear to be associated with filter movement.

    It will occur while I am sitting in the truck monitoring the system over a local network so it isn't associated with something I am doing around the telescope.

    It will be completely absent during a 4 hour imaging run one night but then will start happening the next night when nothing has been changed other than the camera was turned off and then on again.

    I do see the "glow" when I am taking 2 or 3 second flat frames and the darks for the flat frames. Since the 2 or 3 sec. flat darks also have the glow then calibration of the flats eliminates the effect.

    Dean J.
     
  6. Samuel Lising

    Samuel Lising Cyanogen Customer

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    Hi Dean.

    I did some tests last night and found some interesting things.

    I don't have Sky X installed on this particular set up so my results are specific to my set up which uses Maxim and ACP for acquisition. I did some tests that basically acquired images while guiding with short and long guide exposures as well as without guiding. I also acquired images with Maxim only and then with Maxim Through ACP.

    The results from the test showed that when acquiring with just Maxim with guiding on and off, I did not see any glow.

    When guiding with ACP at 1 second guide exposures I had occasional glow and quite faint.

    When guiding with ACP at 10 second guide exposures the glow was more pronounced and frequent.

    When guiding was turned off it seemed that there was little to no glow.

    These tests have to be taken with a grain of salt though - I had a lot of high clouds last night and could not get any clean images. I also only got a handful of images so it's not conclusive. However it did look like that glow disappeared and I'm hopeful that I'm onto something.

    Just wondering if you use the SBIG filter wheel with the built in guider?

    I will need to wait a couple days for the skies to clear but will post more info when I have a chance to take good samples.

    Sam
     
  7. Doug

    Doug Staff Member

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    So far we've never seen this happen in-house.

    If I understand correctly what you're suggesting, sometimes this is present when you power up the camera, and sometimes it is not present? So maybe power cycling the camera would cause it to appear / disappear?

    If that is the case, we'll run some tests to try to reproduce the symptoms. Precise exposure details would also be useful.
     
  8. Samuel Lising

    Samuel Lising Cyanogen Customer

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    Hi Doug.

    Thanks for responding. I'm not sure what you are referring to in terms of powering up the camera. In my set up it is powered up every evening at a remote site. I have similar glow to Dean's results but I have only see the glow in images that I have take over the last 5 months. Before that, the camera was working perfectly for a year and a half. What had changed in my system was software. I had to upgrade to windows 10 and ACP 8.1.

    My results from last night seem promising but I need to confirm when conditions are better. The conclusion I have is that somehow when guiding is on and imaging is being done through ACP, something causes the main CCD to have a glow in the top left corner. In Dean's case, he is using Sky X, but I would like to know if he was using the Self-Guiding Filter wheel to guide when he got his results with glow. Also perhaps he can test his set up with Guiding turned off.

    I'm wondering if there is some problem being caused with the way that image acquisition through applications other than Maxim with guiding is causing this glow.

    I will do some testing in a couple of days when it's clear to confirm if this is true.

    Sorry I didn't include details of exposure and setup. Here they are.

    Equipment:
    SBIG STT-8300 M (latest firmware)
    SBIG FW8G-STT Self-guiding filter wheel

    Software
    ACP 8.1
    Maxim DL 6.13 (with patch)

    Test 1
    Maxim DL Only
    Main CCD - 90 Sec exposure
    Guide CCD - 1 Sec exposure
    Result - No Glow

    Test 2
    Maxim DL Only
    Main CCD - 90 Sec exposure
    Guide CCD - 10 Sec exposure
    Result - No Glow

    Test 3
    ACP controlling Maxim DL
    Main CCD - 90 Sec exposure
    Guide CCD - 1 Sec exposure
    Result - Slight Glow

    Test 4
    ACP controlling Maxim DL
    Main CCD - 90 Sec exposure
    Guide CCD - 1 Sec exposure
    Result - More Visible Glow

    Test 5
    ACP controlling Maxim DL
    Main CCD - 90 Sec exposure
    Guide CCD - Off
    Result - No Glow
     
  9. Doug

    Doug Staff Member

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    So if I understand this, you only see the glow when guiding and using ACP. Correct?

    Also it would appear to be a bit variable? Tes 3 and 4 seem identical but different results?
     
  10. Samuel Lising

    Samuel Lising Cyanogen Customer

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    Sorry test 4 should be:

    Test 4
    ACP controlling Maxim DL
    Main CCD - 90 Sec exposure
    Guide CCD - 10 Sec exposure
    Result - More Visible Glow
     
  11. Dean J.

    Dean J. Standard User

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    Hi Sam, thanks for your work on this issue.

    I do have the FW8G-STT self-guiding filter wheel.

    I also see the glow when I am taking 2 - 3 sec. flats and dark frames for the flats but the only time I have seen the glow for long exposures is when I am guiding on the telescope using The Sky X.

    I have seen the issue on my 360 second and 300 second guided exposures.

    I can take 360 sec and 300 sec dark frames with the camera cooled all day long and not see the glow. It has never occurred to me that the glow might be associated with the guider. I take all of my dark frames with the filter wheel plugged into the camera and the guider's HDMI cable attached to the camera but I have never seen the glow in any dark frames in the 1 1/2 years that I have owned the camera.

    Doug, yes, sometimes the effect is present when I power up the camera and sometimes it is not. Last new moon I used the camera the first night of a 2 night session for guided 300 second exposures for the red and luminance exposures - 4 hours total - with no appearance of the glow. Then the next night I turned on the camera to complete the LRGB series and saw varying degrees of "glow" in the green [5 of 18 exposures] and blue [4 of 18] channels. Two of the examples are posted above. Nothing changed in the camera configuration or the software from one night to the next.

    Dean J.
     
  12. Doug

    Doug Staff Member

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    Samuel that is really great info. It's got me thinking... I may know what's going on. We'll have to do some investigation to confirm.

    When imaging long exposures, the output amplifier on the CCD sensor is powered down to prevent amp glow. It is powered back on and allowed to stabilize briefly just prior to the end of the exposure. Readout proceeds immediately so the amplifier isn't on very long, and the glow is minimized. Any residual glow that might be present would be removed by dark subtraction - both dark and light frames go through an identical sequence so any glow is removed completely.

    Your tests indicate that something is different when using ACP and autoguiding - something that doesn't happen with a dark frame. I have an idea of what that might be.

    When the guider is running, it is operating asynchronously from the main camera - even though it shares electronics with it. At the end of the exposure, it has to stop while the main camera reads out. The last guide exposure is typically aborted so the main camera can go ahead. That is managed inside MaxIm DL's "SBIG Universal" plug-in.

    ACP uses a slightly different end of exposure sequence. It tells MaxIm DL not to proceed with readout until requested. This allows ACP to issue the slew command to go to the next target before the camera downloads. This procedure was adopted because of older generation cameras that held up the computer's processor during camera readout; this would delay the slew command until after CCD readout completed. Since some older cameras (e.g. STL-11000) could take a couple of minutes to read out this was an important optimization - at the time anyway. This allowed the camera readout and the slew to the next target to happen simultaneously.

    More modern cameras like the STT have a full frame store - an internal DRAM memory buffer. Camera readout happens in two independent stages - the CCD sensor reads out directly into the frame store, and once data starts to accumulate the computer can start to read it out. Plus readout on modern cameras is a lot faster, and on top of that MaxIm DL supports threading. In short, ACP doesn't have to wait for the readout to finish.

    I'm thinking that this (probably no longer needed) readout delay feature is the problem. It's delaying the actual start of the readout itself, not just the image download to the PC, resulting in the image sitting there in the CCD chip while amp glow (and extra dark current) accumulates. And apparently when operating in this mode the autoguider isn't being aborted immediately; instead we're waiting for it to finish. Thus your 10 second autoguider exposures caused more amp glow.

    This is what your tests point to. We'll have to confirm it of course, but my theory fits your evidence. It's probably possible to do something in MaxIm DL's SBIG Universal plug-in to prevent this scenario from happening; e.g. when in delayed download mode we abort the autoguider and trigger CCD readout immediately, and just delay image download. But I'm thinking this feature is obsolete anyway. With a faster camera with a full frame buffer and threading in MaxIm DL, we're not waiting on anything. ACP's slew-then-download feature could simply be turned off, and there would be no impact on imaging efficiency and this amp glow issue would be gone. Bob could confirm but I think there's a check box to turn off the slew-then-download feature.

    As for Dean's situation, which is obviously slightly different, it's possible that TheSky X is waiting for the last guider exposure to complete instead of aborting it and getting on with the main camera readout. That would produce the same symptoms.
     
  13. Dean J.

    Dean J. Standard User

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    Doug, thank you. This appears to be a promising line of inquiry and would explain several of my observations - 1. that the glow only appears when I have the camera on the telescope and am actively imaging/guiding; 2. the seemingly random nature of the appearance of the glow in my subexposures; 3. the glow - when it appears - varies in intensity.

    My guiding exposure length is usually 4 to 6 seconds so there are opportunities during a subexposure series for multiple instances of The Sky X waiting for a guider exposure to complete before starting the main camera readout.

    Dean J.
     
  14. Bob Denny

    Bob Denny Cyanogen Customer

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    Thanks for alerting me Doug. I don't monitor the hardware sections here (enough is enough :)). The first thing that comes to mind is "Why 10 second guiding exposures?" That seems long. Are you possibly using the long exposures as a way to regulate the rate at which guiding corrections are being applied? Do you have a 10 sec "Minimum guiding exposure" set in ACP/ If the answer is no then I won't belabor this. If "yes" then I have some feedback for Diffraction.

    Next thing: ACP does have a way to disable the overlapping slew and image download. But I will say that it is an important feature, not historic. Without it, people doing short exposures of many targets (like supernova hunting, monitoring multiple stars in concurrent time series') would come with pitchforks and torches if I disabled it. Even modern cameras take seconds to download, and the big ones maybe 10 seconds. This would badly affect the observing cadence on short exposures of multiple targets. So the feature will stay. To disable it, use the option below:

    Snap2.png

    Furthermore, ACP will attempt to keep the guider running across multiple images. It even has a feature where a series of short images, each of which would fall below the "max unguided exposure length" will be combined for time, and if the aggregate exceeds "maximum unguided exposure length" (user settable), it will run the guider across them all. It also runs the guider across images taken in multiple filters if you tell it that the filters are not in front of the guide sensor. Another feature that has been there for years and is vital to some users, and appreciated by more.

    I think I understand the sequencing Doug described... maybe. Or maybe Doug you can tell me what I need to change in ACP's logic for detecting "end of exposure" and downloading. Note that I don't know anything about the internals of the camera transferring data off the sensor into a possible secondary buffer within the camera... I only know what the camera reports through the MaxIm API. Specifically, if slew/overlap is enabled (in this case CCDCamera.AutoDownload will be True throughout the run, set by ACP at run start):
    1. Start the exposure CCDCamera.Expose()
    2. For exposures of over 1 second, monitor CCDCamera.CameraStatus and wait until it is either 3, 11, or 12
    3. In any case monitor CameraStatus until it is no longer 3 or 12 or when CCDCamera.ReadyForDownload is true. Any of those three will cause monitoring to stop.
    4. Start the slew to the next target
    5. Start the rotator to the next PA
    6. Freeze ACP's other functions, user interface, etc. to cater to cheap/old cameras which are sensitive to CPU load during image download. Give up the CPU essentially.
    7. Start the download of the image CCDCamera.StartDownload()
    8. Wait for CCDCamera.ImageReady = True
    9. Unfreeze ACP
    Error handling makes the above a lot more intricate but if all goes well the above is what happens. For the case where the above checkbox is set (and in this case AutoDownload will be false throughout the run, set by ACP at run start) :
    1. Freeze ACP's other functions, user interface, etc. to cater to cheap/old cameras which are sensitive to CPU load during image download. Give up the CPU essentially.
    2. Start the exposure CCDCamera.Expose()
    3. For exposures of over 1 second, monitor CCDCamera.CameraStatus and wait until it is either 3, 11, or 12
    4. In any case monitor CameraStatus until it is no longer 3 or 12 or when CCDCamera.ImageReady is true. Any of those three will cause monitoring to stop.
    5. Wait for CCDCamera.ImageReady = True
    6. Unfreeze ACP
    I'm unclear of the implications of the above logic on the camera's internals (and I probably should not care, right?) but I am open to suggestions up to but not including special logic for different cameras :) :)
     
  15. Doug

    Doug Staff Member

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    Bob,

    Thanks for the input. I realize this is something deep in the guts of the software and the camera firmware, so it might be a bit confusing. I haven't dug into the code myself, but I do have a very detailed understanding of how these systems all work, and if I had to bet I'd say I put my finger on it. It may be possible to resolve this behavior in the SBIG Universal plug-in.

    I've asked Adam to do some experiments. That will probably take a few days.

    In the meantime, I'd be very interested to hear if someone (Sam!) can do the test where you check "Disable slew during image download".
     
  16. Samuel Lising

    Samuel Lising Cyanogen Customer

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    Hi Bob and Doug.

    Thanks both for responding to this issue.

    Doug, I will definitely test with "disable slew during image download". It's still cloudy at my observatory so it may be another couple of days before I get results.

    I will also confirm the results from my previous tests when it clears up as well.

    Everything you mentioned makes sense and hopefully we are on the right track.

    You mentioned the threading feature in Maxim. I don't have that enabled for either the Main CCD or the Guider CCD. Should this be enabled as well?

    Bob, I stumbled upon the long guide exposure because it was an overcast evening and ACP automatically began to take 10 second guide exposure to to compensate for the low SNR conditions. When I took a look at the images I noticed that there was more glow in the top left corner than with the images that were taken with 1 second guide exposures. This made me realize that the guide ccd (or process) might be part of the problem. ACP is so smart :)

    Sam
     
  17. Doug

    Doug Staff Member

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    Sam,

    Don't change two things at once. Try it with the "disable slew during image download" first. After determining whether that is successful or not, turn on threading and try again. Then try it with threading on and the "disable slew..." off.
     
  18. Samuel Lising

    Samuel Lising Cyanogen Customer

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    Sounds good Doug. I'll let you know how it goes.
    Please let me know if you have any updates on your end.

    Thanks.
    Sam
     
  19. Samuel Lising

    Samuel Lising Cyanogen Customer

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    Hi Doug.

    Good news is that I had about 30 mins in the early evening last night before the roof closed on the observatory due to high humidity. But during that time I managed to image from ACP unguided and got 8 exposures with NO glow. All 8 exposures looked flat and nearly identical. This result made me pretty excited because it means that there is definitely something happening between the Main CCD and the guide process.

    It should be clear tonight, so I will be able to test your theory with "disable slew during image download" enabled. Regardless, of whether this solution works at least we have a good idea of what the problem is now.

    Thanks.
    Sam
     
  20. Samuel Lising

    Samuel Lising Cyanogen Customer

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    Bob and Doug.

    One question. Why do you think that I see this issue after over a year of never having seen it (basically since the camera was new). As I said, the major changes I made to my set up were in January when I installed ACP 8.1 and Windows 10 and this seems to be the time where I am noticing the glow. Additionally there were SBIG firmware and driver updates around that time as well. So essentially 3 major changes that are leading to this issue.

    Bob, were there major changes to the way guiding and image acquisition were happening between ACP 7 and 8? Just wondering because it might give more clear answers on what needs to be addressed with maxim or the camera.

    Thanks.
    Sam
     

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