Resolved AOX Artifact

Discussion in 'Adaptive Optics (AO)' started by Rex Groves, Apr 23, 2020.

  1. Rex Groves

    Rex Groves Standard User

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    We are using a Planewave 20" CDK f6.8 imaging platform. After adding the AOX into our imaging train, we see an oval artifact in the image which we can't identify.

    Our setup WITHOUT the AOX is PW20 > IRF90 > 1.6" Preciseparts spacer > FW8G-STXL> STXL11002. With this we get a nice flat field (via CCDInspector) as seen in the first picture with no artifact

    WITH the AOX the setup is PW20 > IRF90 > 0.6" Preciseparts spacer > AOX > FW8G-STXL > STXL11002 . We decreased the length of the spacer by 1" since the AOX added back focus of 1". As you can see, the oval artifact appears

    Does anyone have any clues for us as to the cause?

    Rex Groves and Al Acker Screen Shot 2020-04-23 at 7.56.53 AM.png Screen Shot 2020-04-23 at 9.09.03 AM.png












    Screen Shot 2020-04-23 at 7.56.53 AM.png Screen Shot 2020-04-23 at 9.09.03 AM.png
     
  2. Colin Haig

    Colin Haig Staff Member

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    Thanks for contacting us.

    Can you provide:
    a) a photo of your setup
    b) Serial number of AO-X, camera, filter wheel. When and where you bought it.
    c) FITS version of these images. Please use WeTransfer/Dropbox/Google Drive as the images will be quite large.
    d) Take a flat field in FITS and send as well.
    e) What filters you have and were using.
    f) What software are you using to drive the AO-X?
    g) Is the AO-X engaged during these "ovals", or is it idle?
    h) does the AO exercise routine tip/tilt it properly in all 4 directions?
    i) any reducers or other optics in the setup? (I think not from what you've said, but sometimes people forget reducers/flatenners etc.)
    j) has the PreciseParts adapter got a matte finish or is it shiny inside? Just thinking about odd internal reflections.
    k) where'd the dust-donut go?
    l) did you remove the packing foam the protects the optical puck (round glass window that tips/tilts) during shipping? (am sure you did, but gotta ask).

    Will ask my colleague @Doug to chime in as well.
     
  3. Rex Groves

    Rex Groves Standard User

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    Thank you

    Here is the link to the dropbox photos

    https://www.dropbox.com/sh/ib87m5lfqtmtzb5/AAAotXW1f0A2aJ5GBNoKZuqda?dl=0

    a) Photo of setup is in Dropbox
    b) Serial numbers are in Dropbox. Each were bought new from SBIG but unsure of dates (AOX in the last year and Camera/Filter Wheel in the past 5 yrs)
    c) Raw RGB FITS are in Dropbox
    d) RAW RGB Flats are in Dropbox
    e) Filters were stock filters that came with the camera - Oval appears even when using the empty filter slot of the filter wheel
    f) Software used is TheSkyX Version 10.5.0 Build 12503 with camera add-on. Using TheSkyX to drive all components
    g) Ovals occur when AO-X engaged or disengaged
    h) Visual evidence during AOX exercise shows normal movement
    i) No other reducers or optics
    j) Precise Parts adapter is matte finish
    k) Dust donut appeared during one of our AOX/no AOX test for oval
    l) Visual shows no packing and picture is in Dropbox

    Rex and Al
     
    Last edited: Apr 24, 2020
  4. Colin Haig

    Colin Haig Staff Member

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    Honestly, I'm stumped on this one.
    I've gone back to it a couple times, and it just doesn't make a lot of sense.

    Have you guys tried using CCDops (free from our site) or MaxIm DL (a 30 day demo is available) to compare results?
    I noticed the images were produced with TSX daily build 12439, not 12503.
    Have you asked on the Bisque forum in case they have ideas?

    In the grasping at straws category:
    When's the last time you baked the desiccant ?
    Cleaned the AO-X and filters?
    Tried with narrowband filters?
    Flipped the AO-X over (not sure this is possible but put the other side toward scope?)
    Am wondering if it is some weird reflection...
     
  5. Doug

    Doug Staff Member

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    From the serial numbers, your equipment was manufactured in 2013.

    Looking at the FITS flat field frames you provided, there is one very obvious anomaly - the vignetting pattern is nowhere near centered. In fact the brightest part of the image is near the bottom. It makes me wonder if you have some kind of major alignment or collimation issue with the telescope. That is something you should check.

    Aside from that, it might be a reflection of some kind. I would recommend trying a baffle in front of the AO-X. As an experiment take a piece of cardboard, cut it to fit inside the drawtube, and also cut a round hole in the middle of it. Basically produce a donut with about 1 cm width all around. Stick that in the drawtube immediately in front of the AO and try imaging again.
     
  6. Colin Haig

    Colin Haig Staff Member

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    Spinning the rotator around would move the pattern.
     
  7. Doug

    Doug Staff Member

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    Yes, if the problem is on the telescope side, spinning the rotator would change the pattern. If the problem is on the AO-X/focuser/camera side, it (most likely) will not.
     
  8. Rex Groves

    Rex Groves Standard User

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    Thanks Colin and Doug

    1) We baked the desiccant 2 weeks ago to see if that was the cause - no impact on artifact
    2) We haven't cleaned the AOX and filters - the artifact is there in the empty filter positions
    3) Flipping - I'm unsure what you mean here
    4) Didn't try narrowband filters but that was because the artifact was there in the empty filter portions
    5) Spinning the rotator electronically (and thus the AOX) maintains the position of the artifact on the image
    6) We cleaned the scope mirror - no impact on artifact
    7) We removed the telescope baffle tube - no impact on artifact
    8) CCDInspector showed dead nuts alignment and flat field of scope/camera alignment before we added AOX - After adding AOX we still see excellent alignment but increased curvature. Adapter may not have been perfectly placed from the chip

    The counts on the image are low, so we will look for a reflection.

    It only pops up when we used the shorter Precise Parts adapter and AOX

    We will try the baffle and see what happens

    It's the little things:)


    Rex
     
  9. Colin Haig

    Colin Haig Staff Member

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    CCDInspector is showing me 32% field curvature, which is huge. The vignetting is not symmeterical - check the corners.
     
  10. Rex Groves

    Rex Groves Standard User

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    Thanks Colin

    I want to check that out closely. In addition, we may have made a discovery last night. We disabled the power to the AOX and the artifact disappeared. We hypothesize that there is a light leak from the red AOX LED into the housing assembly. We're going to check that out today. If that cleans up, I'll check out the field curvature again

    Rex
     
  11. Colin Haig

    Colin Haig Staff Member

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    Black vinyl electrical tape comes in handy for these sort of things.
    Do you think it's coming from the interior of the AO-X? Let us know, we'll want to have our manufacturing people check this.
     
  12. Doug

    Doug Staff Member

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    Seems unlikely that the LED light could leak out inside the package. The back side of the LED is opaque.

    Make sure that you reassembled the shell correctly, with the pieces nestled inside each other so that there isn't a gap on the periphery of the unit.
     
  13. Rex Groves

    Rex Groves Standard User

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    So strange as it is, the LED appeared to be the source of the artifact. We taped the area around the base of the LED with electrical tape and it all cleared up. That was an unlikely scenario!

    Thank you all for your attention to this.

    Rex
     
  14. Doug

    Doug Staff Member

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    Truly weird. Marked as resolved.
     
  15. Colin Haig

    Colin Haig Staff Member

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    For completeness, did you take a photo of your tape hack and a FITS image of the resolve situation?
     

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