Deutsch  Photographic eyepiece projection 
The photographic eyepiece projection First you compute the angle of vision the sun appears without using a telescope: (b1): tan α/2 = [Rs * (fok –1)] / fob * B or (b2): α = 2 arctan [Rs * (fok –1) / fob * B] = 0,545° , with α = visual angle of vision the sun appears without using a telescope fob = 1000 mm (objective focal length of my telescope) fok = 9.5 mm (eyepiece focal length of my telescope) R_{s} = 78 mm (measured radius of the sun picture in photo) B = 140 mm (image intercept of my arrangement) R_{e }= 1.496 * 10^{11} m (earth's orbit) With the relationship (b3): D_{s} = 2πα * R_{e} /360° I calculate a sun diameter of Ds = 1.424 * 10^{9} m. Back to Determination of the sun's diameter 

Copyright by Hans Joachim Ilgen since 1950 