Astronomical Definitions

हिंदी में पढ़ने के लिए यहाँ क्लिक करें 

Declination, is the angular position north or south of celestial equation. Also known as Celestial latitude.

Declination is measured in degrees, minutes of arc, and seconds of arc.

Celestial longitude, measured around the celestial equation, is known as the right ascension right ascension is measured not in degrees, but in hours, with 24 hours of right ascension (to distinguish from 24 hours of time) equal to 360 degrees.

Celestial Poles

The Celestial Sphere "rotates" on the Celestial Axis, which goes through earth’s north and south poles and extends out to the Celestial Sphere intersecting it at the North Celestial Pole (NCP) and the south Celestial Pole (SCP).

Ecliptic

The ecliptic is the path that the Sun appears to trace among the stars in a year because of the Earth's revolution around it. The constellations of the Zodiac lie along the ecliptic.

Zodiac

The zodiac is a circle of twelve 30° divisions of celestial longitude that are centered upon the ecliptic: the apparent path of the Sun across the celestial sphere over the course of the year. The paths of the Moon and visible planets also remain close to the ecliptic, within the belt of the zodiac, which extends 8-9° north or south of the ecliptic, as measured in celestial latitude.

The Tropical Zodiac

The Tropical Zodiac measures 12 portions of 30 degrees each beginning from the Vernal (spring) Equinox. The Vernal Equinox is the point where the Sun crosses the equator on its way North. This is the first day of spring and is 0 degrees Aries

Sidereal Zodiac
In regards to rasi or Signs, the Sidereal Zodiac is made up of 30 degree positions beginning with the Nakshatra of Aswini as measured from certain fixed stars. Since astrologers use different fixed stars to determine the first point of Sidereal Aries, we have different Ayanamshas.

Movable and fixed zodiacs

The "ayanamsa" is the distance or the difference at present moment of time between the fixed and movable Zodiac. The Hindu system of astrology is known as Nirayana System because

The Niryana and the Sayana zodiacs coincided in the year 285 AD when the ayanamsha was zero. At the rate of precession of equinoxes 50.26 seconds per year, the ayanamsha today is 24°03'58".

The equinoctial precession completes one round in aproximately 26,000 years, as mentioned earlier, so that the fixed and movable zodiacs coincide regularly after this time span.

Altitude Azimuth Nadir Celescial Meridian

The altitude of a point on the celestial sphere is defined as the angular distance measured positive toward the astronomical zenith from the astronomical horizon along the great circle passing through the point and the astronomical zenith.

Azimuth

The azimuth of a point on the celestial sphere is defined as the angular distance measured towards the east, from north, along the astronomical horizon to the intersection of the great circle passing through the point and the astronomical zenith with the astronomical horizon.

·         altitude, i.e. how far above the horizon to look for an object, from zero degrees at the horizon to 90 degrees at the zenith.

·         Azimuth, i.e., the direction towards the horizon one must face to look up from the horizon to the object.

In this system we start from 0 degrees for the north meridian, then 90 degrees for due east, etc.

·         Zenith as that point directly above you, defined as the pole of the horizon.

·         Nadir as that point directly below you -- opposite zenith.

·          

·         Meridian-

·         The Meridian is an imaginary circle passing through the Zenith and NCP and SCP and is always perpendicular to the horizon.

·         The line that extends from the north point on the horizon upwards through the zenith and then downward to the south point on the horizon. 

Perihelion

The point at which a planet is closest is called perihelion. The perihelion is the point in the orbit of a planet, asteroid, comet or other Sun-orbiting body where it is nearest to the Sun. It is the opposite of aphelion, which is the point where the orbit of the object is farthest from the Sun.

Aphelion

The point at which a planet is farthest is called aphelion. The point in the orbit of a planet or other celestial body where it is farthest from the Sun.

Apogee

The point in its orbit around the earth when the moon or an artificial satellite is at its greatest distance from the earth.

Perigee

The point in its orbit around the earth when the moon or an artificial satellite is nearest the earth.

Ayanamsa also called ayanabhāga, is the Sanskrit term in Indian astronomy for the amount of precession.In astrology, this is the longitudinal difference between the Tropical (Sāyana) and Sidereal (Nirayana) zodiacs