FW8G not showing guide stars

Discussion in 'Filter Wheels' started by Al Ryan, Aug 1, 2019.

  1. Al Ryan

    Al Ryan Cyanogen Customer

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    We operate a public observatory in a fairly dark sky area that's open once a month. We are all volunteers who travel up to 2 hours to get there so our time is limited. We purchased an SXTL 16200 monochrome camera, a Self-Guided Filter Wheel and AO-X just over two years ago. The main chip gives an image but we have never been able to obtain a guide star. Correction, sometimes we can locate a guide star if binned at 3 for at least 7 seconds. Obviously no good and we thought it was something we did wrong on the sporadic times we were able to work on it. We worked on this problem for so long that the two year warranty expired without us realizing how long we had been trying to deal with the issue on the rare occasions we were able to get there and work on it. One of us (me) has the exact same imaging train at home and has never had a problem even though my location is under suburban skies.

    Looking at other posts about not getting a guide star, we were advised to describe the problem in detail and upload our settings file and a guide image. We were about to do that, but decided to perform one more test. First we tried a number of different HDMI cables with no effect. We put the HDMI cable on my imaging train and I still got guide stars. We put my imaging train on the observatory telescope and had a window full of available guide stars. We then put the front half of my filter wheel (including the AO-X unit) onto the observatory camera and rear half of the filter wheel and got no guide stars. To us, it appears we have a problem located in the rear half of the filter wheel, although I suppose one could argue that this doesn't disprove the problem could lie in both halves of the filter wheel.

    Are there other possible explanations or is that sufficient to conclude the filter wheel should be sent back for repair or replacement?
    -Al Ryan
    Muddy Run Observatory
     
  2. Colin Haig

    Colin Haig Staff Member

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    There are several other possible explanations.
    You should have contacted us right away when you first had the problem - we're known for good service. Two years with a "problem" is an awfully long time. Is there an original message about this here somewhere that you could point me to?

    You'll want to do some tests using CCDOPS or MaxIm DL.

    Try this:
    1. Confirm you have selected "Dual Chip Mode" - this tells the STXL-16200 that it has a sensor connected via the Remote Guide Head port.
    2. Take the camera off the scope, and let light hit the pick-off mirror. Take an exposure with the guide camera. Save the FITS. It should have non-zero pixels. If you use a flashlight, then it should have close to all white (65535) pixels. Attach the FITS image here using the Upload a File button to the lower right.

    If you get a white image from the guide chip, we know its working.
    If it is not working, then it will have to come in for service.
    Do you see or hear the little shutter move?

    If it is working, then the problem is likely the position of the pick-off mirror in the light cone of the telescope, and whether it is focused.
    You may have to dial it right in, and make sure the mirror is getting starlight.

    Can you provide a bit of info on your setup?
    A photo of the setup would help.
    Specifically:
    Telescope specs ? eg Meade 16inch f/10
    Focuser ? Make and model
    Rotator ? Make and model
    How is the "stack" attached. eg. AO-X is attached to the focuser/rotator using the supplied dovetail, or a precise parts adapter, bungee cord and duct tape, how?
    Software and version. e.g. MaxIm DL 6.20

    Let's go from there.
     
  3. Doug

    Doug Staff Member

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    Also please post a FITS frame taken with your guide sensor.
     
  4. Al Ryan

    Al Ryan Cyanogen Customer

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    Hope to be able to go through this and post the files before the weekend is over. Thanks.
    -Al
     
  5. Al Ryan

    Al Ryan Cyanogen Customer

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    The Dual Chip Mode is selected and external guider is selected. We took two short exposures, binned at 1x and 2x and they are attached. The pixels are at 65535 on the 2x and vary, but not by much, on the 1x, which appears to show some sort of interference-like pattern. We got a white image from the guide chip, as we always have. We did not see nor hear the little shutter move.
    Our Setup:
    PlaneWave CDK14 f/7.2
    PlaneWave Hedrick electronic focuser
    No rotator. On a German Equatorial Mount (Paramount ME II)
    From the focuser, we have an STXL Adapter, then the AO-X, then the Self-Guided Filter Wheel and then the STXL 16200 (Using USB for now). No bungee cords or duct tape. If I recall correctly, the Adapter was purchased from PlaneWave and not for Precise Parts. Using Maxim DL 6.20 for imaging and testing and SkyX for selecting (can't get Maxim's to move the Bisque Paramount after a plate solve using the Ascom telescope driver, but not a current concern.) A poor photo of the imaging train is attached.
     

    Attached Files:

  6. Colin Haig

    Colin Haig Staff Member

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    Al, what happens if you take a Dark and Bias on the Autoguider's sensor (camera 2).
    Can you post them here?


    The reason you are having a problmem wiht plate solve / move is because you've got the focal length, aperature, and area of the scope and guide scope set to ZERO !
    Somebody forgot to go into Settings... Site and Optics tab, and fill that in.
    Also, for the focal length entry for the guider, it will be 0.7x the focal length of the main telescope, due to the focal reducer in the self-guiding filter wheel.
     
  7. Al Ryan

    Al Ryan Cyanogen Customer

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    I will take them and post as soon as I can get back there again.
    Thanks for the How To on the plate solving/move. I had been fiddlng around with the SkyX settings and getting nowhere.
    -Al
     
  8. Al Ryan

    Al Ryan Cyanogen Customer

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    Uploaded are a bias and dark fit files using Camera 2.
    My site and Optics tab was filled in- had checked the Load main scope box. It had the wrong focal length which I corrected, but I am unsure if I use the same aperture and obstruction as with the main scope.
    I couldn't remotely check whether this made a difference in the scope moving after a plate solve as the dome is not opening remotely yet. And I still need to get back to the observatory and again check on the guide chip shutter. I may have not been focused on checking this last time.

    One other thing, we recently added a webcam and can view the observatory with it from external software. Maxim recognizes it in Setup and Status but it doesn't add a tab for it. My identical system at home always had a webcam tab and was fully functional once I added a webcam to check the position of the scope relative to the dome. I'll post it in a different section if you want to limit this thread.
     

    Attached Files:

  9. Doug

    Doug Staff Member

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    You have to turn the webcam tab on. There’s a setting for this on the Setup tab.
     
  10. Colin Haig

    Colin Haig Staff Member

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    Use the same aperture and obstruction as the main scope; the focal length with be 0.7x the main scope focal length.
     
  11. Colin Haig

    Colin Haig Staff Member

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    Definitely looks like a hardware problem.
    Was wanting a 1 second dark like the light; but the dark is saturated at 10 minutes; so possibly the shutter has failed.
    The bias level is not right - it's all zero.

    I think our Califonia-based SBIG service and repair wizard @Bill is going to need to get in the loop.
    You can reach him by email: bill (at) sbig (dot) com
    He may chime in here a bit later today.
     
  12. Al Ryan

    Al Ryan Cyanogen Customer

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    Thanks Colin. If I don't hear from Bill today, I'll email him and point to this thread.
     
  13. Al Ryan

    Al Ryan Cyanogen Customer

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    Doug,
    Duh! Thanks. Staring at me and I didn't see it.
    -Al
     
  14. Al Ryan

    Al Ryan Cyanogen Customer

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    Bill Lynch made changes to the camera offset and now we get guide stars. Only one clear night so far to check. In MaximDL, received a camera error after first image in a sequence downloaded. Didn't note the error, intending to try again on next available night. Switched over then to SkyX and everything worked well with a sequence and had no camera error.
    Thanks Bill
    -Al
     

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