Resolved STXL 16200 has intermittent bad frames (mount issue)

Discussion in 'STX and STXL Series Cameras' started by Michael Marino, Sep 24, 2020.

Tags:
  1. Michael Marino

    Michael Marino Standard User

    Joined:
    Apr 21, 2020
    Messages:
    6
    My first post here, please help. My STXL 16200 has started to intermittently download bad frames. I use DSS to stack my data and it reports that the frame is unstackable (no transformation from reference frame). About 1/3 of my 4 minute frames where unusable during the last few nights out. This makes for a very long night. Is anyone familiar with this issue and what I can do to resolve it? Thanks so much...
     
    Michael Marino, Sep 24, 2020
    #1
  2. Colin Haig

    Colin Haig Staff Member

    Joined:
    Oct 27, 2014
    Messages:
    7,409
    Location:
    Earth
    Welcome, Michael.
    Can you provide some information on the following:

    What software are you using to acquire the images?

    What is a "bad frame"? e.g. stars trailed, dark image, no stars showing,... need a bit more specific information.

    Can you use the [Upload a File button] at the lower right to attach a sample?

    What changed from when it worked to now? e.g. a Windows upgrade?
     
    Colin Haig, Sep 24, 2020
    #2
  3. Doug

    Doug Staff Member

    Joined:
    Sep 25, 2014
    Messages:
    9,956
    Yes we'll definitely want to see a bad frame. Raw, completely unprocessed FITS file, please.

    Also please tell us your camera's serial number.
     
    Doug, Sep 24, 2020
    #3
  4. Michael Marino

    Michael Marino Standard User

    Joined:
    Apr 21, 2020
    Messages:
    6
    Gentlemen:
    Thank you for the quick replies. I purchased the camera, SN X18100005, in May from OPT. I used Astrophotography Tool version 3.82 to acquire the data. I recently noticed the problem after shooting longer frames (4-5 minutes). I have also connected an ethernet cable to it, for future use on my network. The bad frames seem to occur in a pattern, with up to three occurring in a row.
     

    Attached Files:

    Michael Marino, Sep 25, 2020
    #4
  5. Colin Haig

    Colin Haig Staff Member

    Joined:
    Oct 27, 2014
    Messages:
    7,409
    Location:
    Earth
    Michael, to me this looks like the mount isn't being guided and the stars are trailing, and this is not a camera defect.
     
    Colin Haig, Sep 25, 2020
    #5
  6. Michael Marino

    Michael Marino Standard User

    Joined:
    Apr 21, 2020
    Messages:
    6
    Colin: My previous upload was a bad frame, this is a "good frame" from the same session. The stars look good to me. You are correct, I am not guiding, but why do 2/3 of my frames look like this one and a 1/3 look like the bad frame? The rig is on a permanent pier mount.
     

    Attached Files:

    Michael Marino, Sep 25, 2020
    #6
  7. Doug

    Doug Staff Member

    Joined:
    Sep 25, 2014
    Messages:
    9,956
    That image is also trailed, just not as much as the first one. This is very typical of telescope mount periodic error.

    Periodic error in a telescope drive goes through a repeating pattern, often (but not always) on a 4 minute cycle. Usually as the next tooth in the worm engages the drive speeds up causing faster trailing. Then the drift is slower through the rest of the cycle.

    You need to either fix the mount's periodic error (many have a PEC feature), or you need to guide your images.
     
    Doug, Sep 25, 2020
    #7
  8. Michael Marino

    Michael Marino Standard User

    Joined:
    Apr 21, 2020
    Messages:
    6
    Doug: Thank you for diagnosing my condition. I'll address those issues and try again. I'm pretty new to the hobby, so I really do appreciate you guys! Thanks for your help.
     
    Michael Marino, Sep 25, 2020
    #8
  9. Colin Haig

    Colin Haig Staff Member

    Joined:
    Oct 27, 2014
    Messages:
    7,409
    Location:
    Earth
    Michael, this is part of the learning curve we all go through.

    The high-end mounts like the Astro-Physics and Software Bisque Paramounts will let you run unguided for about 15-20 minutes if perfectly polar aligned. The mid-price and lower end mounts require guiding.

    If you zoom in about 400-800% into the images, you will see the stars are trailed and there are some discontinuities, caused by periodic error and the normal imperfections in the worm gear/worm wheel.

    Seeing conditions have an impact as well, but your issues are predominantly caused by the mount.
    I'm curious, which mount do you have?
     
    Colin Haig, Sep 25, 2020
    #9
  10. Michael Marino

    Michael Marino Standard User

    Joined:
    Apr 21, 2020
    Messages:
    6
    Colin: I have a Celestron CGXL, which is belt driven. I'm assuming the same principal applies. I haven't done anything to the mount, except polar align it. If someone has experience with the PEC on that mount, I'd love to hear from them. I'm sure my polar alignment can be improved upon, as well.
     
    Michael Marino, Sep 25, 2020
    #10
  11. Colin Haig

    Colin Haig Staff Member

    Joined:
    Oct 27, 2014
    Messages:
    7,409
    Location:
    Earth
    There's a lengthy and involved thread on Cloudy Nights about some tools and things people have done to try to improve the CGX-L.
    https://www.cloudynights.com/topic/678306-celestron-cgx-l-mount-with-ra-harmonic-belt-drive-issue/

    Software wise, check out PEMPro and PECTool.

    The belt goes from the motor to the worm gear. The worm gear turns the worm wheel.
    So you get the added bonus of slop and belt misalignment and flexing, added to the worm gear imperfections, periodic error from the motor gears, the belt pulleys, and then the worm gear. Then the worm wheel too.
    It's hours of fun :)
     
    Colin Haig, Sep 25, 2020
    #11
  12. Michael Marino

    Michael Marino Standard User

    Joined:
    Apr 21, 2020
    Messages:
    6
    I got it. Every tiny baby step has been hours of fun. Thanks again!
     
    Michael Marino, Sep 25, 2020
    #12
  13. Tim Povlick

    Tim Povlick Cyanogen Customer

    Joined:
    May 8, 2020
    Messages:
    321
    Location:
    Kayenta Utah, USA
    Would an AO-8 correct the belt problem or at least "greatly" reduce it?
     
    Tim Povlick, Sep 25, 2020
    #13
  14. Doug

    Doug Staff Member

    Joined:
    Sep 25, 2014
    Messages:
    9,956
    Yes the AO-8 can completely remove that.
     
    Doug, Sep 25, 2020
    #14

Share This Page