 # Finding Distance between the observers using ISS Transit

Yesterday morning was ISS-Solar transit in Lahore, Pakistan

My friend Roshaan Nadeem was in zaman park and I was at my home.

We both used telescopes and captured International Space Station (ISS) pass. See how ISS trails were differently viewed on the solar surface! ?

I used the basic step of the distance ladder which astronomers use for distance measurement. This time, the variable was not the distance to the object, it was the distance between the observing sites. The parallax method says 13km and Google Maps says 12.7km ?✨ Quite close! Isn’t?

This is the beauty of science. It always gets the same answer no matter if you believe in it or not ? Everything was done just by using images as data.

### How to Calculate Distance between the viewing locations using images?

Solar Angular Diameter = AD = 0.52 degrees
% Angular Separation on Screen = 42.95%
Parallax Angle = P = 0.225 degrees
P shift = P/2 = 0.112 degrees
Radius of Earth = R = 6371 km
Altitude of ISS = h = 421 km
Distance between locations = D = ?

Formula for Parallax Method: tan (P/2) = D/(R+h)
Rearranging for D:
D = (R+h) * tan (P/2)
D = (6371 + 421) * tan (0.225/2)
D = 6792 + tan (0.112)
D = 13 km

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