STX-16803 Shutter Misaligned, Shutter Motor Noise

Discussion in 'STX and STXL Series Cameras' started by Russell Croman, May 21, 2020.

  1. Russell Croman

    Russell Croman Cyanogen Customer

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    Hi,

    Just received my STX-16803, wondering if the shutter has an issue. Before and after each exposure, there is a fairly loud 500Hz tone coming from the shutter motor... seems like it's working hard. Also, during the exposure, the shutter opening is misaligned with the camera body opening. See attached picture.

    Is this normal?

    Thanks,

    Russ
     

    Attached Files:

  2. Doug

    Doug Staff Member

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    The voltage to the motor is pulsed to control the power dissipation. It may make some noise as a result.

    @Tim can comment on the alignment.
     
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  3. Russell Croman

    Russell Croman Cyanogen Customer

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    Looking forward to that. Is the shutter alignment field-adjustable? I noticed a couple of trim pots on the circuit board near the connector to the shutter drive motor.

    The motor noise is quite loud... I wouldn't want be sitting near the camera while imaging. Seems like maybe the firmware could stop driving the shutter motor once it's done moving the curtain.

    -Russ
     
    Last edited: May 21, 2020
  4. Doug

    Doug Staff Member

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    Do NOT turn any trim pots! They don't have anything to do with the shutter.
     
  5. Russell Croman

    Russell Croman Cyanogen Customer

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    I wouldn't dream of it without specific guidance.

    -Russ
     
  6. Russell Croman

    Russell Croman Cyanogen Customer

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    I'm also less worried about shutter alignment now... once I installed the filter wheel, it's clear that the filter aperture will vignette before the shutter does. It just caught my eye as I was running the camera through its paces.

    -Russ
     
  7. Tim

    Tim Staff Member

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    Shutter alignment is not an issue unless it starts encroaching on the FOV of the CCD sensor.
     
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  8. Russell Croman

    Russell Croman Cyanogen Customer

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    I'm seeing quite a bit of scatter from just-out-of-view stars on my setup. They primarily only appear on one side of the image. I saw this when I first started using the setup, but I had only one very bright star (Deneb) near the chip, so I figured it was limited to that particular image composition. After many images on many targets, however, it's clear that it is showing up in every image. Here's an example image of M31 with the stars removed to make the problem more evident. Scattering artifacts are colored red.

    STX-16803 Scatter.jpg

    I'm posting this on this thread because the shutter misalignment seems like one possible cause. At first I thought it might be diffraction off of the edge of the SC-3 pick-off mirror assembly, but the locations of the streaks exceed its dimensions, so it's most likely something else. I forget which side of the chip the misaligned shutter encroaches on, but it might be the left side. It's clearly in the imaging train behind the rotator since the streaks always show up on this side of the chip.

    Reminder on the optical train: Tak FSQ-106, NiteCrawler Focuser/Rotator, SideWinder, AO-X, SC-3, FW7-STX, STX-16803.

    Thoughts?

    Thanks,

    Russ
     
  9. Russell Croman

    Russell Croman Cyanogen Customer

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    Here is the same image superimposed on the FOV indicator in TheSky... almost every streak can be traced to a bright star on the left. The really bright one is from my guide star.

    -Russ


    STX-16803 Scatter w FOV.jpg
     
  10. Doug

    Doug Staff Member

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    I don't see how that could be caused by the shutter.
     
  11. Russell Croman

    Russell Croman Cyanogen Customer

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    Any other ideas?

    -Russ
     
  12. Doug

    Doug Staff Member

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    Light is clearly scattering off of something. Given how large the spike is, I think it’s well in front of the camera. But it’s really hard to know. If you can take the camera off and look in...
     
  13. Russell Croman

    Russell Croman Cyanogen Customer

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    It also has to be a straight edge. The only things that fit that description are the filter holder, the filters, the FW7 case, the camera case, CCD chamber window edge.

    Nothing looks odd looking down the OTA. Shining a light in, I can see all the way to the sensor.

    Maybe it's a reflection off of the edge of the filter? Here is the M31 image again, but in color. It looks to me like the further out of view the bright star is, the further *in* the artifact is, which is what makes me suspect reflection rather than diffraction...

    STX-16803 M31 Scatter.jpeg

    -Russ
     
  14. Doug

    Doug Staff Member

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    Try putting a simple baffle in front of the camera aperture.
     

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