Resolved SBIG 11002 STLX with FW8G STXL problem

Discussion in 'STX and STXL' started by Amedeo, Apr 22, 2019.

  1. Amedeo

    Amedeo Standard User

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    Dear SBIG's Tech suport,
    I'm Amedeo Tagliaferri and I've purchased a new CCD SBIG 11002 STXL within FW8G-STXL.
    My astrophoto setup is: Takahashi FSQ106-EDX4 with Moonlite NITECRAWLER 3,5" and SBIG11002+FW8G-STXL.
    I have an obstruction problem with FW8G.
    I've searched for this kind of problem on internet but nothing. So I have made many tests and now I'm sure that the problem is FW8G with its revolver. All the tests below are fullspectrum without any filter.
    I've made a first test without the FW8G connecting the CCD directly to the focuser, assured that all was on focus and take a flatfield frame and you can see the result here (http://www.deepskyimaging.it/wp-content/uploads/2019/04/Flatframe-only-CCD.jpg). The flatfield frame is correct for 106FSQ about the vignetting.
    So I tested connecting the FW8G and assured to be on focus and take another flatfield frame and you can see the result here (http://www.deepskyimaging.it/wp-content/uploads/2019/04/flatframe-with-CCD-FilterWheel.jpg).
    This flatfield frame it's not good for the scope because I noticed an obstruction due to the revolver paired with this scope.
    So I've made another frame, now a light frame, on a starry field with FW8G mounted and no filter, and you can see the result here (http://www.deepskyimaging.it/wp-content/uploads/2019/04/lightframe-with-CCD-FilterWheel.jpg).
    As you can see I haven't a normal vignetting but something like obstruction. Tha flat in this case goes about well but remaining some artifacts in the corner that I can't agree with this kind of scope and CCD setup.
    Please let me know asap what's the solution and if anyone have reported the same problem.

    Best regards,
    Amedeo Tagliaferri
     
  2. Amedeo

    Amedeo Standard User

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    Dear SBIG's Tech suport,
    I'm Amedeo Tagliaferri and I've purchased a new CCD SBIG 11002 STXL within FW8G-STXL.
    My astrophoto setup is: Takahashi FSQ106-EDX4 with Moonlite NITECRAWLER 3,5" and SBIG11002+FW8G-STXL.
    I have an obstruction problem with FW8G.
    I've searched for this kind of problem on internet but nothing. So I have made many tests and now I'm sure that the problem is FW8G with its revolver. All the tests below are fullspectrum without any filter.
    I've made a first test without the FW8G connecting the CCD directly to the focuser, assured that all was on focus and take a flatfield frame and you can see the result here (http://www.deepskyimaging.it/wp-content/uploads/2019/04/Flatframe-only-CCD.jpg). The flatfield frame is correct for 106FSQ about the vignetting.
    So I tested connecting the FW8G and assured to be on focus and take another flatfield frame and you can see the result here (http://www.deepskyimaging.it/wp-content/uploads/2019/04/flatframe-with-CCD-FilterWheel.jpg).
    This flatfield frame it's not good for the scope because I noticed an obstruction due to the revolver paired with this scope.
    So I've made another frame, now a light frame, on a starry field with FW8G mounted and no filter, and you can see the result here (http://www.deepskyimaging.it/wp-content/uploads/2019/04/lightframe-with-CCD-FilterWheel.jpg).
    As you can see I haven't a normal vignetting but something like obstruction. Tha flat in this case goes about well but remaining some artifacts in the corner that I can't agree with this kind of scope and CCD setup.
    Please let me know asap what's the solution and if anyone have reported the same problem.

    Best regards,
    Amedeo Tagliaferri
     
  3. Doug

    Doug Staff Member

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    All things are a compromise.

    The clear aperture of the FW8-STXL is 47 mm. The diagonal of the KAI-11002 sensor is 43.3 mm. The wheel is about 32 mm away from the sensor (I don't have the exact number handy at the moment). Given this it will not vignette with an approximately f/8.5 beam. The f/5 beam of an FSQ-106 will vignette to some extent.

    Yes we could use square 50 mm filters, but the filters are more expensive and the wheel would have to be larger and more expensive also. So it really is a cost trade-off.

    People who want the ultimate field area with no vignetting will spend the money on an STX-16803 / FW7-STX and 50 mm square filters. People who are a bit more budget-minded will go with the STXL-11002 and the smaller, less expensive filters and wheel.
     
  4. Amedeo

    Amedeo Standard User

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    I believe that it is your responsibility to specify in the technical data what you wrote on this topic. In fact I would not have spent around 10500 euros to have this problem.
    I would have spent more for not having this problem if you specify in the technical data !!!
    Now that you have clarified everything, can I change the SBIG 11002 + FW8G with an STX 16800 with a suitable filter wheel ?
     
  5. Doug

    Doug Staff Member

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    This is why we have dealers. They help customers make appropriate choices for their equipment and application. Have you discussed your issues with your dealer?
     
  6. Amedeo

    Amedeo Standard User

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    Can i match the sbig 11002 STXL with the FW7 -STX ?
     
  7. Doug

    Doug Staff Member

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    Not without some modification. Although they look similar, the STX has a different mounting arrangement for the filter wheel than the STXL.

    Can this not be resolved by appropriately using flat-field frames?
     
  8. Amedeo

    Amedeo Standard User

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    Unfortunately the flat frame cannot correct an obstruction !
    The flat frame can only correct the vignetting but what we see is a light obstruction in the four corners.....
     
  9. Doug

    Doug Staff Member

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    Could you post a FITS frame of your flat field?
     
  10. Amedeo

    Amedeo Standard User

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    However surely tomorrow I will contact the dealer !
    I am completely disappointed !!!
    Someone will have to take responsibility !
    Thanks
     
  11. Amedeo

    Amedeo Standard User

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  12. Doug

    Doug Staff Member

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    It's down 10% in the corners. That's not obstructed; it should flat-field out.
     
  13. Amedeo

    Amedeo Standard User

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  14. Doug

    Doug Staff Member

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    JPEG is not informative due to screen stretch. Please send FITS.
     
  15. Amedeo

    Amedeo Standard User

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  16. Doug

    Doug Staff Member

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    That is normal vignetting.

    Inserting a 3 mm filter changes the optical path by 1 mm; effectively refocusing the instrument. It will definitely have an effect on the flat-field.

    Please try calibrating a light frame with a suitable set of calibration frames - flat, light, dark, flat-dark (bias is okay instead of flat-dark if it is a very short flat exposure).
     
  17. Amedeo

    Amedeo Standard User

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    CLS Astronomik filter is 1 mm !
     
  18. Amedeo

    Amedeo Standard User

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    Ok I'll try as soon as I can !
     
  19. Amedeo

    Amedeo Standard User

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    I just did a test and the flat filed worked great, correcting the vignetting !
    So thank you Doug for the support ;)
     

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