Creating FOV Indicator in TheSkyX for StarChaser

Discussion in 'Guiding and Adaptive Optics - StarChaser and AO' started by John Cangelosi, Nov 15, 2022.

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  1. John Cangelosi

    John Cangelosi Standard User

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    Hello,
    I've been getting good results with my StarChaser 2 OAG but I'd like to set up a field of view indicator for it in The Sky X.
    I have a FOV indicator for my STF-8300M camera but I'm unsure of the offset (and position) from the CCD view to the view from the SC2. If anyone has any tips or advice that would be greatly appreciated.
    -John
     
    John Cangelosi, Nov 15, 2022
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  2. Colin Haig

    Colin Haig Staff Member

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    You might try pointing at a star-rich field, then take images with both SC-2 and main camera. Then platesolve both images to get astrometric coordinates and orientation.
    The SC-2 has an array of 1280 x 1024 pixels that are 4.8um square. No focal reducer built in. The pick-off mirror will flip the image orientation.
     
    Colin Haig, Nov 15, 2022
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  3. John Cangelosi

    John Cangelosi Standard User

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    Plate solving both placed the SC2 in the center of my STF 8300 FOVI- does that sound correct?
    Thank you
     
    John Cangelosi, Nov 21, 2022
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  4. Colin Haig

    Colin Haig Staff Member

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    The result you should expect would put the SC-2 just outside of the main camera field, centred left-to-right along one edge.

    It would be correct only if your pick off mirror is dead centre in the middle of the 8300, which would cast a big shadow on the main chip, and defeat the point.
    Maybe send over the two FITS light frames and I can have a look if i get a spare minute.
     
    Colin Haig, Nov 21, 2022
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  5. John Cangelosi

    John Cangelosi Standard User

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    Thanks, upon further inspection I think I was just centering both instead of using the coordinates. When I used the coordinates they look very far apart so I'll try again the next clear night just to make sure I have two files of the same area.
     
    John Cangelosi, Nov 21, 2022
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  6. Colin Haig

    Colin Haig Staff Member

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    I had a very fast look.

    1. Please fix focal length of the guider.

    Guider FITS file, I see this:
    FOCALLEN = 2100. / SBIGFITSEXT Telescope focal length in mm

    It should be set the same as the main camera focal length. The main image has:
    FOCALLEN = 2450. / SBIGFITSEXT Telescope focal length in mm

    The SC-2 does not have a focal reducer in the optical path; so it has the same focal length as the main camera/scope.
    e.g. if your scope is 12-inch f/8.1, then it should have the same parameters for both the main camera's scope and the autoguider's scope.

    Since you're using TheSkyX to capture these images, you'll need to fix that through the Autoguider equipment setup.

    2. Plate solved focal length
    Using MaxIm's Analyze PinPoint astrometric plate solving with the ATLAS-REFCAT2 catalog, I get 2439-2444 for the focal length for both images.
    So that is in close agreement to the 2450 number. Of course as the focuser repositions during the night, this will move around a few mm, depending on the thermal expansion/contraction of the OTA etc.

    3. Plate coordinates
    I get:
    Main - Light clear 2x2 NGC133
    RA 00h 32m 01.8s, Dec +63° 25' 22.7"
    Pos Angle +211° 27.2', FL 2439.1 mm, 0.91"/Pixel

    Guider - 00019580 NGC133
    RA 00h 30m 00.3s, Dec +63° 01' 56.6"
    Pos Angle +211° 29.5' (R), FL 2444.9 mm, 0.81"/Pixel
    This is mirror-imaged.

    4. TSX version
    They're up to 10.5.0 13479
    You might want to update.
     
    Colin Haig, Nov 21, 2022
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