For RA, there is no such natural starting point - in fact any point on the globe would work as well as any other, take your pick. Selecting a starting point for RA introduces us to another term in astronomy called the ecliptic . For this to happen, it means that the equator must cross the ecliptic in two places. Astronomers selected one of them and decided that 0h RA would be the point at which the ecliptic crosses the celestial equator in the constellation of Pisces, a point called The First Point of Aries . From that point, RA increases toward the east .
Precession Wait a minute.
Well, it turns out that when astronomers decided to name a starting point for right ascension 2,000 years ago, The First Point of Aries really was in Aries, but the intersection has crept into Pisces over the intervening years due to a slow shift in the Earth's orientation relative to the heavens. The slow shift is called precession , which has been compared to the wobbling of a top as it slows down. Precession is also responsible for us having to rename a pole star every 12 to 14 thousand years, alternating between the likes of Polaris and Vega. The main issue concerning precession for the FVG program is that I had to learn what it meant since the databases at the ADC contained different values for the celestial coordinates of the same objects. Not hardly, since RA and DE really only gives us 2 dimensions, and it takes 3 dimensions to define a point in 3 space.