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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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