Question

How is parallax calculated?

Answer 1

See below

Explanation:

There is two parallax to be calculated: the daily and yearly parrallax

Daily parallax is used to measure distance to satelites and is calculated as follows `p´´=a·sigma/(Dsin1´´)` where a is mayor semi axis Earth-Sun, D the distance to satelite from Earth, `sigma` is a correcction due to no sphericity of Earth and `p´´` is given in seconds of arc.

The yearly parallax is used to calculate distance to starts and in calculated by

`p´´=(lambda+omega-lambda+omega)/2` where `lambda, omega` are respectively the longitude of Earth and star in ecuatorial coordinates in the rigth moment they differ in 90º or 270º