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)
Rs = 78 mm (measured radius of the sun picture in photo)
B = 140 mm (image intercept of my arrangement)
Re = 1.496 * 1011 m (earth's orbit)

With the relationship (b3): Ds = 2πα * Re /360°
I calculate a sun diameter of Ds = 1.424 * 109 m.


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