ST-i Autoguiding Drift

Discussion in 'Legacy Models - Community Support' started by Scott Ballard, Aug 22, 2017.

  1. Scott Ballard

    Scott Ballard Standard User

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    Hello,

    I purchased the ST-i mono as a guide camera this year and have used it about four to five times.

    It has improved the quality of my images, but I'm wondering if I can do more to reduce some apparent drift I'm seeing.

    The typical procedure I use is to establish comm link, calibrate, then set up the autoguide. I'm using a Celestron CGEM mount with a 10 inch Meade SCT. Using a 100mm celestron guide scope attached with ADM accessories. All of this is mounted on a concrete/steel pier.

    Every time I've used the ST-i as a guider, one of the axis holds tight, and the other axis slowly drifts as seen in the screen shot I've attached. Sometimes the drifting axis is the "X", other times it's the "Y".

    Any help or ideas would be appreciated!
     

    Attached Files:

  2. Doug

    Doug Staff Member

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    It should not drift at all. Can you post a screenshot of your calibration results dialog?
     
  3. Scott Ballard

    Scott Ballard Standard User

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    I don't have any immediately, I'll have to capture some the next time I'm out observing. It could take up to a month.
     
  4. Scott Ballard

    Scott Ballard Standard User

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    I just want to make sure there is no issue with the cable connection. The attached image shows the diagram from the ST-i manual and the CGEM manual. Thanks.
     

    Attached Files:

  5. Doug

    Doug Staff Member

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    Two comments:

    1. You can build RJ-12 cables two ways - with the wires flipped in the middle, or not.
    2. These RJ-12 cables aren't exactly the most robust; they can get broken fairly easily.
     
  6. Scott Ballard

    Scott Ballard Standard User

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    So, it seems I was able to avoid drift this time by just repeating the calibration enough times that it finally gives me the "cross" shape for the X and Y axis of motion. I'm guessing when the calibration only gives one of the two dimensions, then it's not calibrated correctly. I attached an example of both scenarios.

    Does anyone know if software like Carte du Ciel would interfere with guiding to cause drift or failure of calibration? We use Carte du Ciel to make fine targeting adjustments on our CGEM.

    Also, when you're setting up the calibration, what does the "declination" setting do? It doesn't seem to have any effect.


    2 with declination set 15.jpg after flip dec set to 0.jpg
     

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