Staff Assigned: Bill Lynch Sensor tilt on STL11000

Discussion in 'Legacy Models - Community Support' started by Tom Blahovici, Feb 28, 2020.

  1. Tom Blahovici

    Tom Blahovici Standard User

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    Hi
    There is a tilt in the imaging plane which causes out of round starts at one location on the CCD. I have struggled with this ever since I obtained the telescope and camera for several years. It is always at the same location on the chip.
    The telescope is a Takahashi FSQ106ED. I have replaced the original configuration of a camera rotator from Tak, as well as the focuser. These were replaced by a Starlight Instrument focuser (4") and a Pyxis 3" diameter rotator. Yet, I still have the tilt. The tilt is always in the same location even if I manually rotate the camera. Thus it would appear that the tilt is coming from the camera itself.
    No I understand that I can send this to Bill, but seeing that I had this from day 1, perhaps the factory alignment will not necessarily correct the issue.
    So my question is, can the camera mounting plate be shimmed to correct for this? How could I do such a thing? What do the shims look like?
    I see that there are several tilt adapters available on the market these days and some cameras now have this built in.. Are there any that can just go on the nose piece of the camera? Back focus is also an issue I guess.
    Thanks for any suggestions.
    Tom
     
    Tom Blahovici, Feb 28, 2020
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  2. Colin Haig

    Colin Haig Staff Member

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    On my personal STL-11000M, there is a small shim washer under the plate that attaches to the beige face of the camera on just one of the screws, giving a small amount of tilt to correct for machining tolerances.
    Our expert @Bill may be able to test and adjust for this.
     
    Colin Haig, Feb 28, 2020
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  3. Tom Blahovici

    Tom Blahovici Standard User

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    Hi,
    Ok, so it's a washer. My STL11000 has 2 of them according to the documentation that came with the camera. Perhaps I can buy these and try myself. At the moment I just crop the field. I've learned to live with it. Good to know.
    Thanks, Tom
     
    Tom Blahovici, Feb 28, 2020
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  4. Bill

    Bill SBIG Service and Repairs Staff Member

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    What size, on the documentation, are the "shims"? Where are they located? Are they in there?

    -Bill
     
    Bill, Feb 28, 2020
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  5. Tom Blahovici

    Tom Blahovici Standard User

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    Hi, The shims are at position b (.005") and position c (.01). I can't determine if they are there, but having never removed the nose piece I would think so.
    So I do have a license for CCDInspector.
    Also, I looked on McMaster Carr, and they have steel washers for shimming. The mininum ID is 0.25. In stainless they have 0.375 ID.
    So would this just be a matter of adding or removing shims until I find a good setting with CCDInspector? I plan to do this when the snow is gone up here...

    Thanks.
     
    Tom Blahovici, Feb 28, 2020
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  6. Colin Haig

    Colin Haig Staff Member

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    Tom, you could use Upload a File (down to the right) to upload a FITS image of a starfield for us to take a look at. If the file is too big, you could use DropBox or Google Drive or WeTransfer.
    Generally these are accurately set at the factory, so it may be something else in your optical train. Feel free to post a photo of your setup.
     
    Colin Haig, Feb 28, 2020
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  7. Doug

    Doug Staff Member

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    Yes we use McMaster Carr SS shims.

    We use specialized test equipment to measure and correct the tilt, but you should be able to achieve the same thing with CCDInspector.
     
    Doug, Feb 28, 2020
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  8. Tom Blahovici

    Tom Blahovici Standard User

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    Hi,
    Here's a photo of the telescope. You will need to zoom in.
     

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    Tom Blahovici, Feb 28, 2020
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  9. Tom Blahovici

    Tom Blahovici Standard User

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    I'm having trouble with tjhe fits...I tried to make it to a jpg.
    The tilt is in the upper left of the photo. It doesn't change with any position of the telescope. It is definitely not sag.
    Where would that correspond to on the chip, if you are looking at the camera with the nose piece closest to you?
    Thanks.
     

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    Tom Blahovici, Feb 28, 2020
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  10. Colin Haig

    Colin Haig Staff Member

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    I can't do any analysis on the JPG.
    CCD Inspector is showing me tilt across the left side, but its a tiny 1 arcsecond amount.
    I need an unprocessed light frame in FITS format.

    What's the blue thing in the photo? Some kind of rotator?
    How is the camera coupled to it?
     
    Colin Haig, Feb 28, 2020
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  11. Colin Haig

    Colin Haig Staff Member

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    Also, is there a focal reducer in there?
     
    Colin Haig, Feb 28, 2020
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  12. Tom Blahovici

    Tom Blahovici Standard User

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    Hi,
    The telescope has the focuser, and starlight instruments actually had the adapter that goes to the Optec Pyxsis 3" rotator (the blue thing). They made sure that the adapter was square with the focuser. The adapter is from Optec and it is a dovetail groove held in place by special bolts. No focal reducer.
    As to the fits, I tried uploading it to my server and it won't let me. It's a non-supported type.
    1 arc second? Is that enough to cause an issue? Because it is there.
    Here's the file in a zip folder. It's completely non-processed. No darks or anything.
    Thanks, Tom
     

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    Tom Blahovici, Feb 28, 2020
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  13. Colin Haig

    Colin Haig Staff Member

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    Thanks for the image.
    It's as if the collimation of the whole setup is off. Stars in that upper left are particularly oval; If it was camera tilted a bit, I would expect a similar effect in the opposite side of the field.
    e.g. the optical centre isn't aligned with the centre of the CCD.

    Some detective work is going to be needed... suggestions:

    Set filter wheel to an empty slot to eliminate any distortions from extra glass in the mix.
    Home the rotator to PA=0. Make sure the camera is aligned with PA=0. Rows along RA, columns in DEC.
    Take an image. Set the rotator to 180. Take an image. Compare. If CCD inspector gives same results, eg the left side stars are oval in the same direction, then its camera attachment to the rotator. You could loosend the camera faceplat and tuck some shim stock under neath so you dont have to fully remove the shim washers etc.

    Another idea:
    In software (eg MaxIm) open both, rotate the 2nd 180 and subtact the images to see how far out they are. If everything is rotating dead-centre perfectly, then you'd know all is perfect.

    This is what I get in CCD Inspector; I had to add the focal length and aperture as TheSkyX didnt put it in the FITS file. You might want to check if you have your FOVIs and instrument settings done in TSX.
    tom_b_stl.png
     
    Colin Haig, Feb 28, 2020
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  14. Tom Blahovici

    Tom Blahovici Standard User

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    Hi
    Thanks. I'll give it a shot on the first clear night, in about 2 days.
    Any suggestions as to which corner of the ccd should be shimmed? 4 possibilities here...
    Thanks
     
    Tom Blahovici, Feb 28, 2020
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  15. Colin Haig

    Colin Haig Staff Member

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    Not 4 possibilities. The plate that is on the face of the camera has only 3 screws :) though in your experimenting, you might shim 1 or 2 of them, so a total of 6.
     
    Colin Haig, Feb 29, 2020
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  16. Bill

    Bill SBIG Service and Repairs Staff Member

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    Here are a couple of thoughts on ways you could begin. 1) You could remove the shims altogether and see what you get with no shims or 2) You could remove the .01 from position C and put it under B. Or vice versa. Or pull B and leave C...

    -Bill
     
    Bill, Feb 29, 2020
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  17. Tom Blahovici

    Tom Blahovici Standard User

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    Hi,
    I think I am going to have to wait a bit.
    I live in Montreal and I have three feet of snow on the ground. It's also around 10F at the moment.... The scope is permanently set up outdoors but once the cover is removed it's exposed to the elements. A little tough to manage this at the moment without gloves.
    What I will do in the mean time, is to fully characterize the tilt. See what effect rotation has, see if it is centered. That I can do until the weather improves a bit. I'll post updates as I go.
    Just to be sure, the shims that are currently there are washers correct? I wouldn't want to lose them.
    Thanks for all the help.
    Regards, Tom
     
    Tom Blahovici, Feb 29, 2020
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  18. Tom Blahovici

    Tom Blahovici Standard User

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    Oh, Even though I have this tilt, cropping the final images to remove the top left corner does give nice photos nonetheless. Here's the latest image from a few days ago. 9 hours total. It's unfortunate though that I need to do this, with a scope like the FSQ and the full frame sensor.
     

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    Tom Blahovici, Feb 29, 2020
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  19. Doug

    Doug Staff Member

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    Spectacular!
     
    Doug, Feb 29, 2020
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  20. Tom Blahovici

    Tom Blahovici Standard User

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    Time for an update here.... I thought about where I want to go in the future with my setup and came to the conclusion that the combination of the STL11000 and Pyxis Rotator just limits anything I would like to do in terms of backfocus. There is only about 1/2" left. Therefore I cannot use a tilt adapter, an on axis guider like the SC-2 and so on. Thus, I have ordered a MoonLite NiteCrawler for my FSQ106. This has the integrated rotator and I get almost 3" of backfocus liberated.
    I should get this in a couple of weeks, and will then investigate the tilt with the integrated tilt adapter. A much better solution for the future.
    I hope that SBIG comes out with a Sony IMX455 based camera soon, so I can stay with SBIG!!
     
    Tom Blahovici, Apr 18, 2020
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