STT 8300M Guider Camera Inoperative

Discussion in 'STT Series' started by jerryyyyy, Jun 11, 2018.

  1. jerryyyyy

    jerryyyyy Cyanogen Customer

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    Hi,

    Over a couple days my guide camera has stopped working. I am away from the observatory and can get the main imager to run fine but not the guide chip camera. Produces salt and pepper images. We changed out the HDML cable.

    Rob suggests:

    the other possibility is that the guider shutter is not always opening. the shutter is controlled by a small DC motor that turns until it hits a stop. on the motor shaft there’s a little paddle that’s supposed to hit the stop, and it is connected to the shaft with a set screw, which can come loose. if that happens you won’t hear any click-clack from the guider shutter, just a motor spinning noise.

    Do you have any diagrams that would relate to this possible fix, so I can find the screw. Does not seem to be in filter wheel manual.

    JY
     
  2. jerryyyyy

    jerryyyyy Cyanogen Customer

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    Owen or Others, I sent this to Bill but he is out until next week,

    I tried to get the guider chip to work with Rob’s help and we seem to be shooting blanks. My best guess at this point is the guider chip has gone bad. I changed out the HDMI cable. I would like to check everything possible to make sure it is not a software problem.

    What I see in Maxim is:

    Camera 2 Information:

    Could not acquire target.

    Could not find target star.

    Guide star not found.


    This is not surprising because when I try to take a guider image it shows an even field of grey. I get the same if I shoot using the SBIG software. Yesterday if I tried to expose in the guider and at times I seemed to see the stars at night and it might try to guide for a couple cycles then I would just see a blank.


    Since you are out tonight I will try to run the ACP calibration script again… I think this will get all the software settings straight. If it does not run and again I get the blank image, I am left with the bad chip.


    I can take the camera off the scope and do bench testing and look at the screw in the shutter. I have to take if off to send it anyhow. Yesterday at times I heard the guider shutter click with Rob on the phone, but then it went silent on me.


    A mystery.. of course when the sky is clear and the moon is new.


    JY



    PS Will cross post over at Diffraction Unlimited to see if Owen or anyone else has an idea.
     

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  3. Colin Haig

    Colin Haig Staff Member

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    Jerry, red circle I think is the small screw, it looks ok. What I don't like the look of is the scratch along the side of the mechanism where the long threaded shaft is (red ellipse).
    FWG Shutter Screw smallCH.jpg
     
  4. Doug

    Doug Staff Member

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    Can you upload an image from the guide camera in FITS format?
     
  5. jerryyyyy

    jerryyyyy Cyanogen Customer

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    The images when they come in are correct. I fiddled with the screw and also the wires and the problem intermittently comes and goes. Here is the photo of my insides. If there are no insights, will send to Bill tomorrow so he has it next week. I think the serial connection is a weak point and the motor could be burnt out too.... has 5 years solid use. When I hook it up initially it is more likely to run so maybe the motor is on its way out.

    Thanks for responding Colin....
     

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  6. Doug

    Doug Staff Member

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    Intermittent problems can be really hard to figure out. Still useful to upload a "failed" FITS image because I can tell if the CCD is working properly but the shutter isn't.

    Colin, the scratch is simply where the locking screw pushes; when cranked down it tends to score the block a bit. This is normal and won't hurt anything.

    Double-check that the flex cable is plugged in properly; it may just be the photo but it looks skewed.

    Otherwise it may have to go to Bill.
     
  7. jerryyyyy

    jerryyyyy Cyanogen Customer

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    Thanks Doug. I fiddled again with the cables this AM when it was cold. I give up. I am going to send the thing this afternoon and it will travel over the weekend. (I think Bill is back Tuesday and will try to have it arrive then.

    I triple checked that cable. It could be at many levels at this point. This camera has three cables of different ilk attached. If I can easily save and image I'll send it. When the shutter works they are quite different. When it does not work I get a "dark" salt and pepper greyt and when it does work I get my usual "flat" with a couple donuts.
     
  8. Doug

    Doug Staff Member

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    Yes but a “normal” dark or...
     
  9. jerryyyyy

    jerryyyyy Cyanogen Customer

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    Here is a shot. I could get it remotely.
     

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  10. Doug

    Doug Staff Member

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    That's looking pretty normal, so I'm guessing the shutter didn't open.
     
  11. jerryyyyy

    jerryyyyy Cyanogen Customer

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    Hey Doug, Bill fixed the camera... bad wire....

    But, I have another problem. Cannot get the guiding calibration to work right... wanders off the star. We had this problem in the past... remember :)

    I ran both your calibration as well as Bob's and the "L" is not perfectly at right angles. The rates of guiding also seem. Off. Any recollection about what this was? Pier flip turned off. Calibration done at DEC = 0 pointing East. SmallShot.jpg
     
  12. Doug

    Doug Staff Member

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    Is the red line following the star as you do the calibration?
     
  13. jerryyyyy

    jerryyyyy Cyanogen Customer

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    Goes left to right OK but the "Y" is not perpendicular.
     
  14. jerryyyyy

    jerryyyyy Cyanogen Customer

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    Doug, does it matter where the scope is pointing when calibrating? I have the scope pointing East of the meridian: weights on the East and Scope on the West pointing towards the East.

    I talked to George at AP and he said that I need to verify that the mount is working correctly in the X and Y directions, which I will do tonight. Then rerun just your calibration without ACP and get Maxim to work before I add in Bob's script.
     
  15. Doug

    Doug Staff Member

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    Watch it while calibrating and make sure the red line follows the star. If it does than the issue is completely mechanical.

    Put an eyepiece in and move the scope with the slow motion controls. That will eliminate all things electronic and software. You should be able to see any backlash, stiction cycles, etc.

    The thing with German Equatorial mounts is the backlash can be wicked, especially in RA. You want the drive to lift the weight as it tracks, not allow it to fall. If the latter, it will bounce back and forth between the gear teeth and you'll get horrible tracking no matter what you do.

    You can also have declination backlash. If it's large it may impact your guider calibration. Increasing the Cal Time can help compensate for this. There is also a backlash feature that lets you dial it out (best to correct too little than too much!). The anti-stiction feature will also help with the tracking.
     
  16. jerryyyyy

    jerryyyyy Cyanogen Customer

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    Doug, got it to work last night going back to basics. On George's advice I checked the movements in DEC and RA and they are OK.

    I went to 2X on the guider chip as he suggested due to long FL.

    I got the Red L, not perfect but looked OK.

    However, that being said the numbers that come out in the settings seem bizzare to me. Seems the X and Y speeds should be the same that the angle... I have no rotator.

    I plan to try Bob's script tonight to see if it sorts this out. I just ran this in Maxim alone last night after verifying the mount was still OK. Guider at 2X.jpg
     
  17. Doug

    Doug Staff Member

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    There is an option in the software to save your guider calibration images. If you do that you can upload them and we can see if things look reasonable.
     
  18. jerryyyyy

    jerryyyyy Cyanogen Customer

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    Doug, I had that checked... where are they hidden?
     
  19. Doug

    Doug Staff Member

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    Your Documents folder
     
  20. jerryyyyy

    jerryyyyy Cyanogen Customer

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    Found them. Did not look at them but here they are. Will look now.
     

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