Question

What is parallex method

Answer 1

Astronomers estimates the distance of method called parallex method. They also mesure single in arcsecond .

I hope this answer is right

Answer 2

parallax is a method of measuring distance to an object. Similar to how our binocular vision helps us determine distance.... the direction to a distant point is slightly different from two separate observation positions........ 

if the distance between the observation positions is known, and the angle between them can be measured, it is a matter of simple geometry to calculate the distance to the object....
 it is a relatively simple concept but is one of the most important for ...making astronomical observations...      :)