STT-8300M/FW8G-STT guiding glitches

Discussion in 'STT Series (retired)' started by Tony Lazar, Feb 12, 2018.

  1. Tony Lazar

    Tony Lazar Standard User

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    The setup is CCDSoft 5.0, STT-8300M, FW8G-STT, CGE-1100.

    When autoguiding at a fast rate (0.5 sec), the guide star periodically gets very dim for one frame and the guiding jerks in one directon, then recovers to center within a couple of frames. This all happens inside 2 seconds but is enough to streak the stars.

    Trouble is, this is intermittent. I've gone several nights with perfect guiding, excellent centering of the guide star, with as little as 0.3 seconds per guide cycle. Then boom! - it starts misbehaving. (And it's not clouds!)

    Rebooting the whole setup (mount, camera, laptop) sometimes fixes it, but I haven't yet tried to isolate the problem between the three. What am I doing wrong?
     
  2. Doug

    Doug Staff Member

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    Really hard to know without data. Does your software application have any logging features that we/you could use to diagnose this?
     
  3. Tony Lazar

    Tony Lazar Standard User

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    I have several clear nights coming up here in California. Will see if I can log an error, and also isolate between laptop/CCDSoft, STT/FW, and CGE mount. Any one could be misbehaving.
     
  4. Doug

    Doug Staff Member

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    What is your camera's serial number?

    As a starting point, make sure your camera firmware and software is up-to-date. Rather than use SBIG Driver Checker's built-in update feature, download the latest version of the application itself from our web site (Go to the STT camera page and click the Downloads tab). The latest version avoids some potential pitfalls with firmware updates.
     
  5. Tony Lazar

    Tony Lazar Standard User

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    Doug, I’ve isolated the guiding chip problem on the STT-8300M/FW8G-STT. It runs fine for 90% of guide frames, but then randomly one on ten or so guide frames comes up very dim – I estimate at about 10% of normal intensity.

    If I’m guiding on a bright star, the system ploughs through it because 10% of the light is still available for centering (the dim frame sparks with noise as the system tries to auto-contrast the star using available light).

    But if I’m guiding on a dim star, there’s not enough light and the system (rightly) bumps in the direction of the brightest noise, so the next frame comes up way off-center. Sometimes I get two or three dim frames in a row, which really messes up the guiding because the system has nothing to center.

    Otherwise the system behaves perfectly – I’ve made some beautiful pics, but always while guiding on a bright star. There’s no problem with the CGE mount (X and Y are behaving properly) and no problems with CCDSoft.

    Normally I suspect cables in intermittent hardware failures like this, so I pulled and re-seated both the HDMI cable and the DB9/I2C cable between FW and camera body, but no joy. Now I suspect the shutter or exposure mechanism on the FW8G-STT guide chip, but I have no idea how that works.

    As an experiment, I switched chips to guide on the main camera chip (even though you tell us not to do that…) It guides fine, with loud clicks as the mechanical shutter actuates on every frame – so I didn’t leave it in that mode for long. Back with the guide chip, I get no clicks, so I assume it’s an electronic shutter.

    The camera info is in the attached image. Any ideas what to try next?
     

    Attached Files:

  6. Doug

    Doug Staff Member

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    The guide sensor has an electronic shutter, but also a mechanical shutter that is used for dark frames. It should stay open while guiding. I recommend visually confirming this while running a guider sequence.

    Make sure your drivers and firmware are fully up-to-date using the SBIG Driver Checker. Also make sure your driver software is using the latest patched version (don't know if CCDSoft is still maintained?).

    Maybe try the MaxIm DL demo to see if you get the same issue?
     
  7. JoshuaHufford

    JoshuaHufford Cyanogen Customer

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