This is usually defined as the point on the celestial sphere where the plane crosses the prime hour circle ( the hour circle occupied by the First Point of Aries ), also known as the equinox.
12.
Over its year-long journey through the constellations, the Sun crosses the celestial equator from south to north at the First Point of Aries, and from north to south at the First Point of Libra.
13.
The Sun's placement upon the vernal equinox, which occurs annually around 21 March, defines the starting point for measurement, the first degree of which is historically known as the " first point of Aries ".
14.
The Almanac specifies for each whole hour of the year the position on the Earth's surface ( in declination and Greenwich hour angle ) at which the sun, moon, planets and first point of Aries is directly overhead.
15.
An alternate definition is that SHA of a celestial body is the arc of the Equinoctial or the angle at the celestial pole contained between the celestial meridian of the First point of Aries and that through the body, measured westward from Aries.
16.
The First Point of Aries ( also known as the Cusp of Aries ) is so called because, when Hipparchus defined it in 130 BCE, it was located in the western extreme of the constellation of Aries, near its border with ? Arietis.
17.
Ravathi is the Hindu name for Zeta Piscium, a star on the edge of the Hindu sidereal astronomy this star is identified as the First Point of Aries, i . e . when the Sun crosses this star, a new solar year begins.
18.
Because of the precession of the equinoxes, the First Point of Aries has since moved into Aquarius by around 2600 AD . The Sun now appears in Aries from late April through mid May, though the constellation is still associated with the beginning of spring.