What is precession, and how does it affect our view of the heavens?

1 Answer
Apr 8, 2016

In a year, the circumpolar stars, like the Pole Star,. will generate a parallax angle = 5", nearly, over a year, due to Earth's tilt-axis rotation, through the same angle, about the ecliptic normal.


It takes about 258 centuries (Great Year) for one complete precession-rotation of the polar axis about the mean position that is normal to the Earth's orbital plane (ecliptic). This rate is nearly #360/25800^o=0.01395^o= 5 second/year. The parallax is the apparent angular displacement of the circumpolar stars due to the actual displacement of the observer on the Earth..