SBIG FW8G-STXL Self-Guiding Cover

Discussion in 'STX and STXL' started by blackdragon72, Jun 17, 2019.

  1. Colin

    Colin Staff Member

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    Regarding the FW interference: Would it be possible for you to check to see if the 3 silver screws in the central large brass coloured gear are protruding out and up out of the gear? There should be approx. 1 unused thread, and they should be slightly sunk in to the gear. The flat top surface of the gear should be the highest point.
     
  2. blackdragon72

    blackdragon72 Standard User

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    I will double confirm, but if I remember correctly, I did not feel anything when I touched the gear surface last night, so they should not.
     
  3. Doug

    Doug Staff Member

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    That's the only thing either Colin or I could figure as a remote possibility. There's nothing else for the sensor PCB to run into. And the wheels we have here don't get stuck.

    At least it reaches focus without causing any problems.
     
  4. blackdragon72

    blackdragon72 Standard User

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    It is wires. When sensor is extracted all the way out, wires get bent and get caught by the filter screws.
    I dont have any issue when in focus either, since wires are not bent.
     

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  5. blackdragon72

    blackdragon72 Standard User

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    Now I think I am facing the most difficult problem to solve, sensor tilt.

    Apparently the sensor is tilted - I tried a few test and confirmed scope is fine. Does SBIG shim all the CCDs or it is customer's responsibility to shim it? I dont see any shims in standard cover so I assume it was not shimmed.
    Or can I send the CCD back to Bill for shim?
     
  6. Doug

    Doug Staff Member

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    The sensor tile is veri
    Colin has investigated and recommended changing the way the wires are installed so they cannot interfere with the wheel. Thank you for reporting that.
     
  7. Doug

    Doug Staff Member

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    All STX and STXL cameras are checked for sensor tilt at the factory. We have a machine that can measure the sensor tilt extremely accurately. If shims are required then the are located under some of the screws of the front adapter plate. They look like thin washers. There will also be a shim sheet indicating where these shims, if any, are supposed to be located. When you remove the adapter plate to install the filter wheel, the shims need to be moved to the front of the wheel with the adapter plate.

    If your camera's shim sheet indicate none are necessary, or they are required and are installed correctly, then there is a tilt problem elsewhere in your optical system.
     
  8. blackdragon72

    blackdragon72 Standard User

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    I dont see any shim or shim sheet.

    It is from CCD since I rotated CCD 90 degree by changing the bolting direction of 3" accessory rings and stars shape remained the same. If the tile from any component before 3" accessory ring then star shapes would change.
    Do you have any tech support number I can call to discuss this issue?

    Do you have any record to show whether a CCD has shim?
     
  9. blackdragon72

    blackdragon72 Standard User

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    Or could the tilt come from self guided cover?
     
  10. Doug

    Doug Staff Member

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    What is your camera's serial number?
     
  11. blackdragon72

    blackdragon72 Standard User

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    X17110005.

    If it has been shimmed in manufacture then I might have misplaced shim and shim sheet. Is it possible you send shim sheet and same shim to me?
     
  12. blackdragon72

    blackdragon72 Standard User

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    The star trail in image appears to be more top down, so means sensor tilts a bit forwards or backwards.
     
  13. Doug

    Doug Staff Member

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    No shims required on X17110005. Manufactured November 23, 2017. All test data on that camera were excellent.

    It is highly unlikely for the filter wheel to have a tilt - they have excellent machining tolerances. Not sure what is going on there.
     
  14. blackdragon72

    blackdragon72 Standard User

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    Doug,

    Thanks! I will dig further.

    I think Ha filter might be worse than others? Any potential cause why this would happen.
     
  15. blackdragon72

    blackdragon72 Standard User

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    One more question: does SBIG driver restrict cooling to -35C max? I set cooling to -40C in SGPro but it stopped at -35C. I remember seeing somewhere mentioned -35C limit due to CCD window condesation concern.
     
  16. Colin Haig

    Colin Haig Staff Member

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    Yes, it is limited to a sensor temperature of -35C for the STXL-16200 and certain other camera models.
    There are a number of reasons. An important one is to have available reserve cooling capacity - we don't want the thermo-electric cooler running at 100%, because then it can't regulate effectively.
     
  17. blackdragon72

    blackdragon72 Standard User

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    Then why dont you limit the cooling capability to 80% instead?

    I can get to -35C easily for most summer nights (eg, I got -35C with 60% cooling last night) and I expect -50~-60 in winter.

    Does it apply to new Aluma series? I need to think about twice for my next camera. It is more like paying BWM price for a Corolla, then I would rather to save the money for something else, or get a real BMW.
     
  18. Doug

    Doug Staff Member

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    STXL cameras are capable of a 60C delta. That can be too much at low ambient temperatures.

    The minimum temperature for the STXL series is there to prevent condensation in the chamber. At -40C it is cold enough to have a light rime start to form on the sensor, despite the high performance molecular sieve desiccant. This is not good for the sensor or your images.

    A temperature of -35 is safe - and much colder than you need. Even at -20C the dark current of these sensors is exceedingly low, and there isn’t any good reason to go below -30C.

    Also you may start to see an increase in residual bulk image on some sensor models at extremely low temperatures.

    The Aluma models don’t have a programmed lower limit. Despite the exceedingly compact, lightweight package they can achieve a 50C delta. Aluma does not limit your lowest temperature but I would still recommend staying above -40C.
     
  19. blackdragon72

    blackdragon72 Standard User

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    Got it. It will save the battery too. It is 8A at 100% cooling so not many battery can last in winter night.
     
  20. blackdragon72

    blackdragon72 Standard User

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    BTW, it appears to me that lock screw tends to get loose over time. After adjusting prism and sensor location, I want to use some type of glue or tape to fix lock screw to the cover. What is the best option? It should be strong enough so it does not get loose, but also can be easily removed if refocus is needed. I tried tape, it looks messy and does not stay well.
     

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