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    Re: Low Altitude Sun Artificial Horizon Exercise
    From: Bill Ritchie
    Date: 2020 Nov 30, 23:03 +0000
    Using the left image only,  I calculate 245° / 1.7nm Away (+/- 1.6nm) assuming 50°F / 29.8 InHg. That's a great low altitude result from a great photo. Well done.

    But I'm sure I'm missing your point, Greg - how do the callipers improve this?

    Workings. 
    A: Sun Pixel Diam: 343 +/- 4px
    B: UL - UL reflection: 2149 +/- 4px
    C: Sun Diam 32.434'
    Formula: C * B / A.
    Lowest Case Hs: 200.5' = 3° 20.5'
    Highest Case Hs = 206.0' = 3° 26.0'
    Average Case Hs = 203.2' = 3° 23.2' gives 245° / 1.7nm Away.

    Regards
    Bill Ritchie. 50N 003W


        

    On Sun, Nov 29, 2020 at 5:32 PM Greg Rudzinski <NoReply_Rudzinski@fer3.com> wrote:

    This exercise is to show how a plastic digital caliper can accurately measure any low altitude Sun image using the horizontal diameter as the yard stick.

    Image #0759 

    UT 22:16:31    28 November 2020

    Lat. 27° 41.7' N   Lon.  80° 23.9' W  (GPS)

    Diameter of Sun 32.434'   

    What is the azimuth and intercept from GPS ?

    Greg Rudzinski

    The image is using a 135mm vintage lens on a Canon 2000D (24MP). Settings: 1/4000sec, ISO 100, f 16. Sun filtered with double polarizers.

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