FW8G-STT guider focusing issue

Discussion in 'STT Series' started by Brad Bates, Apr 2, 2020.

  1. Brad Bates

    Brad Bates Standard User

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    First time on this forum...on my "obselete camera" :)
    Recently installed my STT 8300M/FW8G on a new 3250mm FL 16" RC telescope. I am having an issue reaching the same focus for both the main imager and the guiding imager. The guider has reached the full in position and still 400 - 500 steps away (FLI-PDF 7000 steps/0.35 inch) from the main imager. I have not had this issue with previous telescope(s) of shorter FL. I don't see anything mechanically wrong inside- guider just at the mechanical limit. (Also the pickoff mirror is as close as I can get it without vignetting the main). Any thoughts?

    Also, searching this forum on this issue, I found another thread on a "random amp glow" issue in the upper left corner that has puzzled me for years. I've had the same experiences 1-2 images out of 30. I'm weeding it out using the sigma reject feature during processing - so it is annoying but not detrimental. Just curious if you've found a repair or firmware update that I could eliminate it?
    Thanks!
    Brad
     
  2. Colin Haig

    Colin Haig Staff Member

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    Hi Brad,
    Welcome aboard.

    Is there a focal reducer and/or field flattener in your setup?
    Since the scope is f/8, I'm a little surprised its not reaching focus on both, and so will ask @Doug to chime.

    The CCD sensor will always have some amount of amp glow in the upper left corner - that's where a readout amplifier is on the chip.
    It's the nature of the ON Semiconductor / Kodak / Truesense KAF-8300 sensor.
    Variability in it should be fairly minimal though.

    Potential causes and resolutions:
    • Hardware issue, including things like aging of the electrolytic capacitors - a trip to @Bill would be needed for any hardware repairs or rework
    • Firmware - timing improvements or adjustments - a few revisions have come out
    • SBIG drivers - we've made updates
    • Application software bugs
    What software are you using?
    Have you tested with CCDops? or MaxIm?

    I'd like to see a couple sample darks and bias frames, both good and symptomatic ones.
    They *must* be in FITS format.
    Use the Upload a File at the lower right to attach them.
    If they are too large, use WeTransfer/Dropbox/Google Drive, to send over.

    Can I get the serial number of your camera and approximately when you bought it (new or used?)

    There have been updates to the SBIG drivers and to the firmware for the STT8300.

    1. Start with the driver update.
    Download the latest version of the SBIG Driver Checker from our website.
    Install it.
    Disconnect the camera USB.
    Update drivers.
    Reboot.
    Log back in, re-attach the camera USB cable.
    Shoot some test images.

    2. Firmware updates.
    In the SBIG driver checker use the Firmware tab to see what firmware is in the camera.
    There have been a few tweaks for the STT. The last one I recall was in November 2019.
    Using the Driver Checker, use the firmware tab.
    Check the firmware first.
    If there is an update, then make sure to keep the camera plugged in, on good AC power, not in the middle of thunderstorms or blackouts ;-)
    Be patient - it can take several minutes

    Note that changes mean that you will need to redo your bias/dark frames used for calibration as the camera behaviour may (will) change.
     
  3. Doug

    Doug Staff Member

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    Seems odd about not being able to parfocalize the guide camera. There's a reasonable amount of adjustability there; I can't imagine your telescope would have so much field curvature to be impossible to focus.

    You say you have the guide camera all the way in... try bringing the pick-off mirror out slightly, i.e. move it towards the guide chip. That will effectively shorten the distance slightly, and should allow you come to focus.
     
  4. Brad Bates

    Brad Bates Standard User

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    Is there a focal reducer and/or field flattener in your setup? No optics in the path.

    What software are you using? Sky X

    Have you tested with CCDops? No or MaxIm? No

    I'd like to see a couple sample darks and bias frames, both good and symptomatic ones. Uploaded sample 1 Bias and 2 Darks. Blinked through all my Bias and Darks since 2013 - no symptomatic Bias or Dark images found. I uploaded a "good" and "bad" Green images you can blink for comparison. On this relatively recent Target (IC 443) I found out of 240 images in my Raw File; 7 filters - I found this issue in all filters: 4 Blue, 3 Green, 7 Ha (1800 sec subframes), 5 Lum, 2 O-III(1800 sec) 3 Red and 1 S-II (1800 sec) subframes. (I can send more....)

    Can I get the serial number of your camera and approximately when you bought it (new or used?) New 12/18/2012 S/N TU100222

    There have been updates to the SBIG drivers and to the firmware for the STT8300....Looks like I last updated my drivers and firmware in 2017. Installed and updated latest drivers and Firmware...

    You say you have the guide camera all the way in... try bringing the pick-off mirror out slightly, i.e. move it towards the guide chip... OK Trying that tonight!

    Thanks All of you for your support! I truly appreciate your help on this discontinued hardware - much appreciated
     

    Attached Files:

  5. Colin Haig

    Colin Haig Staff Member

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    Brad, I've had a fast look. Using MaxIm DL Pro, I did some pixel analysis.
    Green 12316 has an overall background level that is higher than 12315, by a little more than 100 ADU, and this exceeds the amp glow you are seeing in the corner of 12315.
    Because this is sky and not a lab-test with calibrated light sources, am not really sure why the difference.
    bradbates.png

    I suggest you do the firmware and driver updates, and see what you get.
     
  6. Brad Bates

    Brad Bates Standard User

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    Hi Doug,
    Tried your suggestion and that corrected the problem-as well as my understanding of what is going on when adjusting the pickoff mirror. This one is resolved!

    Hi Colin,
    Thanks for looking at this. I did update my camera firmware and drivers. So I am watching new images. I'll upload a better example H-alpha images that have similar backgrounds (FYI) and from the same target/timeframe. I went thru all my flats (my controlled light "Lab test") from the same timeframe and also could not find any other indication. Maybe I should re-run this at lower light exposures?
    Can't think of an external light source that can "only" illuminate one corner of a CCD chip in any rotational angle.
    Are there any internal FW8G-STT light sources that may suggest a return to "@Bill"?
     

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  7. Colin Haig

    Colin Haig Staff Member

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    Any chance that TheSky X is calibrating out the glow?
    ALL of your light frames should have some amount of glow.
    I don't see any in 12010.
     
  8. Brad Bates

    Brad Bates Standard User

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    I'm not sure I understand what you're asking me, these are raw uncalibrated frames, no "autodark" applied. I checked the FITS header just to be sure. I wasn't thinking this was a software issue. I use CCDStack (sorry!) for reviewing raw frames, calibration and processing through Master frame combine.
    So back to your comment on 12010 - Yes! that's my point. For example, out of the 240 raw images taken on this target over several nights, most have no "glow in the upper left corner" at all, but 21 did have a glow that was pronounced enough to me to notice during raw frame review(blinking through all the images). Anyway-maybe the driver and firmware update will take care of this...
    Again, Thanks for your time!!
     
  9. William B

    William B Cyanogen Customer

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    Hi Brad.

    Try programming a short pause between exposures of ~1 min and see if that improves or brings some consistency between frames.

    The amp glow may be residual from the previous frame readout and the variability in the glow that you are seeing 'may' depend on how long the mount/guiding/dither etc took to re-establish and stabilise between the previous frame download completion and the new frame start, thus giving a variable time for ccd cooling to quench any remaining glow.
    By programming a small delay between frames it gives a chance to cool the on-chip readout amplifier before the next frame begins.

    The other thought is that you might have issues with the USB download speed and the frames showing higher levels of amp glow took longer to download than normal. This would be harder to pin down since so many other PC background processes that impact USB speed will be involved. If your camera has built-in USB frame buffers this should not be an issue anyway, sorry but I don't know the internal workings of the STT8300 so this suggestion might be a red-herring.

    William.
     
  10. Brad Bates

    Brad Bates Standard User

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    Thanks William!
    I'll add a delay as well with the updated firmware and drivers-thanks.

    Your last paragraph is interesting to me since I have an older desktop running my observatory. But I've been considering updating it for communication speed from other issues (USB 3.0) so maybe this is related somehow.
    The specs say it has full frame image buffer.
    The specs also say it has an RBI preflash. Anyway this preflash can get to the main image chip? or become a postflash?
     
  11. William B

    William B Cyanogen Customer

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    Shouldn't be problem Brad. I use a different make of camera(s) with the KAF8300 chip and RBI pre-flash is used on those cameras without any apparent issues.
    It is a part of the CCD chip rather than an external add-on so it should not appear at the wrong time during an exposure cycle and RBI pre-flash is applied evenly across the whole chip, not just a corner.

    I read earlier that you are using TheSkyX for capture. Make sure you are up to date with the daily builds.
    The SBIG plug-in that drives the camera in TheSky has been updated and changed quite a few times over the last year or so for bug fixes and that its quite independent of the SBIG hardware drivers that you check manually.

    TheSkyX SBIG plug-in is distributed with the TheSky and can't be (easily) upgraded manually but will be updated when you install the latest daily build.

    I'm wondering if your version of TheSkY sometimes switches the camera into a fast readout mode as that would certainly change amp glow but again I don't know the specifics of STT8300 camera and whether different download speeds are supported.
    My own camera(s) with the KAF8300 do have three download modes, all selectable within TheSky and I have to be careful to select the right mode for the task in hand otherwise I get variable background levels and mismatched calibration frames.

    William.
     
  12. Brad Bates

    Brad Bates Standard User

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    Wow! Thanks for the insights. I have the next three days of clouds and rain to do some research on this-and update. Thanks again William
     

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