What is parallax angle?
For a simple, close up example of parallax, go outside and look at some distant object such as building, tower or even a tree. Hold your hand out with one finger raised and close one eye. Line up your finger so it obscures the object from view. Then close that eye and open the other without moving your arm. Now, move your finger to block that eye’s line of sight. You can then do the math, as they say, and figure out the distance to the object based upon how far apart the two locations of your finger were. This is what a survey crew does to figure out land plot boundaries. When astronomers take a picture in June of a star and then another in December–i.e. 6 month apart or halfway through the Earth’s trip around the Sun–they use this as their baseline for their triangulation calculations. The bigger the baseline, the more accurate the distance estimate.
