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    Re: Sun CN with DSLR Camera Revisited
    From: Greg Rudzinski
    Date: 2011 Oct 5, 08:22 -0700


    You ask:

    "What does your Palm Pilot show for my measurements? BTW: I would not use the filter as a stripe through the middle thus hiding also the horizon directly below the sun. How about covering only this half of the lens where the sun will be and leaving the other part with the horizon unfiltered?"

    The Palm Pilot sight reduction for your pixel count LL,C,UL :

    LL 16* 1.8' Hs (961.8px) intercept 1.0 away azimuth 253.8*
    C 16*17.7'Hs (977.7px) intercept 1.1'
    UL 16*32.9'Hs (992.9px) intercept 1.8'

    Palm Pilot Version 6.9 does not correct for temperature and pressure.

    I have tried various filter arrangements including what you have suggested and settled on the central strip as best to avoid exposure issues from horizon glare and to allow for ease of filter construction. 4 or 5 images are taken for any given CN camera observation then the most perpendicular Sun horizon image is selected. I find this better than edit straightening the image. My version of iPhoto does a poor job at the straightening task.

    The practical method I now use is different than the calibration method to provide aperture and shutter speed flexibility. When calibrating the images are best taken at maximum focal length to get the sharpest possible horizon and body limbs. No need to be this precise for working through regular practical CN camera observations.

    The only time intercepts get large (over 3 moa) is when I try to do a pixel count on an image which is noticeably tilted off perpendicular.

    Greg Rudzinski

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