The Three Primary Astrological Coordinate Systems:
Ecliptic Coordinate System
Equatorial Coordinates
Horizon Coordinate System
Ecliptic Coordinates -- In this system, the ecliptic or plane through the Earth's orbit is taken as the plane of reference. The co-ordinates used are Celestial Latitude (the perpendicular distance of the object from the ecliptic in angular measure) and Celestial Longitude (the angular distance along the ecliptic between the plane through the object and the First Point of Aries). The Solstitial Colure is the great circle which passes through the summer and winter solstices (the hour circle of R.A. 90° and 270°).
Celestial Latitude (Ecliptic Latitude) -- The angular distance of any object measured north or south of the plane of the ecliptic to the poles, from 0° to 90°.
Celestial Longitude (Ecliptic Longitude) -- The angular distance of any object as measured from zero Aries to a plane through an object.
Equatorial Coordinates -- In this system, the Earth's Equator is the plane of reference. The poles are at the intersection of the Earth's pole and the pole of the celestial sphere, an imaginary surface at an infinite distance with the Earth as its center. This is true for all points on the Earth, latitude and longitude. The poles are the North Celestial Pole (NCP) and South Celestial Pole (SCP). The circle at the intersection of the plane of the Earth's equator and the celestial sphere is the Celestial Equator.
Right Ascension (R.A.) -- The angle between an hour circle passing through an object and the meridian plane, in the case of equatorial coordinates, zero degrees of Aries. R.A. is measured eastward on the celestial equator from what is called the True Equinox to the body in question. R.A. is expressed in either degrees (0° to 360°) or in Hours-Minutes-Seconds (0h to 24h).
Declination -- The angular distance of any object measured north or south of the plane of the celestial equator, from 0° to 90°.
Horizon Coordinates -- In this system a plane through the observing point parallel to the horizon is the plane of reference. The poles are the Zenith (point overhead) and the Nadir (point underfoot). The vertical circle through a celestial object (such as a star) and the zenith is the Object Circle. The coordinates are given (for the object) by Azimuth (horizontal angle measured from an arbitrary reference direction -- East in our case -- counterclockwise to the object circle) and the Altitude (elevation angle measured upward from the horizon to the object). The great circle through the north and south points and the zenith is the Meridian, and the great circle through the east and west points and the zenith is the Prime Vertical. Circles of parallel altitude to the horizon that are not great circles are called Almucantars.
Altitude -- The angular distance of any body above or below the plane of the local horizon. Altitude is measured from 0° to 90° from the plane of the horizon to either pole.
Azimuth -- The angle measured around the 360° circumference of the horizon, either east or west (there are different practices). The azimuth of an object as measured from the meridian plane of the observer and a vertical plane through any body.
http://www.astrologysoftware.com/resources/vastrology/vastrology.asp
Coordinate Systems
https://dept.astro.lsa.umich.edu/resources/ugactivities/Labs/coords/
Celestial Coordinates
https://www.youtube.com/watch?v=ih7aGeFKBPE
Introductory Astronomy: Positions on the Celestial Sphere
https://www.youtube.com/watch?v=9XHoVF2G0j8
Astronomy For Astrologers
Part 1
https://www.youtube.com/watch?v=KgmFXmyh_4I&t=164s
Part 2
https://www.youtube.com/watch?v=388uJiLzsEI
Part 3
https://www.youtube.com/watch?v=hZOOkTXVRgA&t=1152s
Part 4
https://www.youtube.com/watch?v=uTMP-g4ZcPw
The Basics – The Ecliptic, The Equator And Coordinate Systems
note:
While we, as astrologers, use Celestial Longitude divided into the Zodiac to define horizontal coordinates, astronomers generally use Right Ascension. As with Celestial Latitude, measurement begins with 0° corresponding to the point of the Vernal Equinox. However, where Celestial Latitude measures counter-clockwise, Right Ascension measures clockwise from this point, with the measurement being expressed either in degrees, minutes, and seconds of arc, or in hours, minutes, and seconds of time. In any event, it is still a system which used the Earth as its center of reference. Why that’s logical and okay for astronomical measurement, but irrational and not okay for astrological measurement is beyond me!
http://astrologyclub.org/ecliptic-equator-coordinate-systems/
I definitely think Right Ascension is logical and okay for astrological measurement, and I have been using Right Ascension in Astrology since 2009.
It's definitely a coordinate that is highly overlooked and dismissed in Astrology.
