Question

How is stellar parallax found?

Answer 1

Observe angular displacement of the star, from the same location, for the duration of N days. This is stellar parallax for the displacement of the observer through N days, in Earth's orbit.

Explanation:

Stellar parallax is the apparent angular displacement of a star , when the observer is displaced.

If this angle is `alpha`, for two observations in time-spacing N days, the distance of the star is

`tan (2piN/365.256363)/tan(alpha/2)` AU
= `2tan (2piN/365.256363)/alpha` AU, nearly.
(If `alpha` is in radians and is quite small, tan `alpha/2` = `alpha/2`, nearly).