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    Re: Digital Image CN Exercise
    From: Greg Rudzinski
    Date: 2010 Apr 14, 04:28 -0700

    Jeremy,

    I,m using a vintage Pentax Super Takumar fixed 200mm for my digital image CN exercises and by trial and error have found the sweet spot for sunset photos above 2 degrees. The problem has been overexposure. The solution seemed to be a pair of circular polarizers but this caused distortion when held at the front of the lens. The better solution has the circular polarizers held out in front of the lens as far as possible. This somehow has greatly reduced distortion. The linked image settings are f16, 1/1000s, ISO 100, B&W, in manual mode. The resulting intercept is a respectable 0.6 NM.

    When you get the chance try taking some telephoto images through your whole horizon Plath using the camera clock as a chronometer. Determine the minutes of arc per pixel for the lens with the Sun's diameter (from high altitude) as reference then count pixels to the nearest limb. This technique works well enough to consider a digital camera scope attachment as an interesting sextant accessory option.

    GRudzinski

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