Erratic Shutter on ST-i

Discussion in 'Specialty Cameras SG-4, AllSky, ST-I' started by wtconner, May 22, 2015.

  1. wtconner

    wtconner Standard User

    Joined:
    Oct 27, 2014
    Messages:
    4
    Location:
    Spencer, IN
    I'm experiencing erratic shutter action with my ST-i c.
    Normally the shutter opens to take a frame then shuts.
    Now it just stays open after a frame unless I have selected a companion dark frame.

    I have checked the EEPROM according to a memo by Jan Soldan.
    The ST-i only has two motor phase values, 0 and 1. I'm currently using 0 since value 1 seems to reverse the shutter action.

    I have written in the motor phase value of zero. But the shutter still does not function normally.

    Any help with understanding this anomaly would be appreciated.

    On occasion the shutter will only open part way, usually 1/4 open so I only get the left hand quarter of the frame. Interesting????

    Bill
    Hale Hill Observatory
     
  2. Bill

    Bill SBIG Service and Repairs Staff Member

    Joined:
    Oct 12, 2014
    Messages:
    484
    Bill,

    It isn't abnormal for the shutter to open for a light frame and stay open if no dark frame is taken. For example, if you are imaging in "focus" mode, the shutter will open (or remain open if it already is) and stay open while it's acquiring images. I would not expect it to open and close with each frame. I'm not sure that it automatically closes after a light frame without a dark, such as a "none" Grab in CCDOps. I'll have to verify that on Monday. Are you sure that shutting every time after taking a light frame is normal?

    A simple test to see if your shutter is functioning properly (and you can do this holding the camera in your hand, looking straight at it) would be to power up and establish a link to the software, my experience is with CCDOps. You should hear the shutter make a clackety clack sound. I'm not sure if the shutter will be open or closed at this point. Then grab an "also" image, .12 seconds is enough to see what is going on. If the shutter is closed after connecting, it should open for the light (I believe the light is first) and close for the dark and stay closed, two moves. If it was open, it should stay open for the light and then close for the dark and stay closed, 1 move. Then Grab a 2nd "also", you should see it open and close regardless of the initial shutter position. Then, if the shutter is closed, Grab a "none", watch it open, I think it will stay open. Grab an "only", it should close. I think it will stay closed. I'd be interested in what you find.

    There is no need to mess with the motor phase, I've built many a ST-i, from a tray of parts up to a completed functioning camera, and have never set the motor phase. The partial opening would be of more concern to me. The times it opened partially, was that while grabbing an image? What drew your attention to the partial opening? Someone once told me that their shutter was partially open when the camera was de-energized. The shutter is free to move when the camera is powered down so it may or may not be open, closed or anywhere in between.

    Regards,

    Bill
     
  3. wtconner

    wtconner Standard User

    Joined:
    Oct 27, 2014
    Messages:
    4
    Location:
    Spencer, IN
    Bill, thanks for the prompt review. You are accurately describing what I am observing the ST-i shutter doing. Perhaps I was wrong about "normal" operation.
    The shutter opening only partially occurred when I was trying to image with my ST8300M, using the ST-i as guider. When the ST-i frame downloaded I noted only part of the frame was exposed and the rest was black.
    I pulled the ST-i and looked into it and noted the shutter was stuck partially open. The weather was cold at the time (February) so it may have been accumulated moisture that froze and caused the malfunction.
    The equipment is exposed to ambient temperature and humidity all the time since it is in my observatory that is not heated or cooled.
    Should I take the ST-i apart and clean the shutter area??? I'll need specific instructions if so.
    Thanks
    Bill
     
  4. Bill

    Bill SBIG Service and Repairs Staff Member

    Joined:
    Oct 12, 2014
    Messages:
    484
    No Bill, I wouldn't recommend that. Perhaps this might be more of a one time thing, type thing. If it becomes increasingly problematic then call or email me at work and we can talk about what might be best. You might consider doing something to protect it in the more extreme conditions. No sense letting the elements eat it up prematurely.

    -Bill
     

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