7 articles for "Horizon"

**Horizon**[Prima]

The visible or apparent horizon is the circle formed where the sky above the observer meets the Earth.

The rational or true horizon is a great circle parallel to the visible horizon whose plane goes through the center of the Earth.

The celestial horizon is the rational horizon extended infinitely into space to intersect the celestial sphere.

See also:

♦ Celestial Horizon ♦ Great Circle ♦ Celestial Sphere ♦ Rational Horizon

**Horizon**[Munkasey M.]

A Great Circle of the Celestial Sphere. This term iscommonly used in one of four different ways, which are:

**1. The Visible Horizon:**

This is the horizon that we see when we have an orientation to Earth. It is our view of where the Earth and the sky meet in the far distance.

**2. The Sensible Horizon:**

This is the extension of the visible horizon to the limits of the Celestial Sphere.

**3. The Rational Horizon:**

This is the same as the sensible horizon, but the sensible horizon taken from the center of the Earth and not at the Earth's surface.

**4. The Celestial Horizon:**

A combination of the sensible and the rational horizons taken at an infinite distance. **This is the horizon which is used in astrological calculations.**

See also:

♦ Celestial Horizon ♦ Great Circle ♦ Celestial Sphere ♦ Rational Horizon

**Horizon**[DeVore]

The circle round the Earth that separates the visible and the invisible hemispheres. The terms sensible, visible or physical horizon are often employed, indicating the line which terminates our vision, where the celestial bodies appear and disappear. The astronomical horizon, termed the rational horizon, is obtained by supposing a line drawn from the Earth's center parallel with the horizon. Astrologically, the eastern horizon is the degree rising in the east, and the Sign then appearing is the Rising Sign.

See also:

♦ Celestial Horizon ♦ Great Circle ♦ Celestial Sphere ♦ Rational Horizon

**Horizon House System**[Astro*Index]

Also called the Zenith House System. A pseudo-House System in which the lunes (pseudo- houses) are formed by *great circle*s which pass through the *Zenith* and *Nadir* (rather than the North and South points along the Horizon), beginning with the *Meridian* and progressing toward the eastern half of the *Prime Vertical*. Each pseudo-house is of the same size; i.e., each *lune* is exactly 30° in size. The *MC* and 10th cusps are the same. But, the *ASC* is not the cusp of the 1st house; instead, the intersection of the Ecliptic with the eastern half of the Prime Vertical is used. This point is known, variously, as the *Vertex*, or Electrical Ascendant. American astrologer Charles Jayne preferred the Campanus House System, but advised serious investigation of the Zenith (or Horizon) System. A Campanus Table of Houses may be used the compute the house cusps for the Horizon System: Add 12h to the given Sidereal Time, determine the tabular values for the colatitude of the given place, and add 180° to the longitudes obtained.

E x a m p l e: Given that: obl = +23.45° LAT = +37.00° ST = 07:32:00 = 113.00° Then, ST' = 19:32:00 = 293.00° COLAT = 90° - LAT = +53.00° and from a Campanus Table of Houses: 10: CAP 21°16.6' 11: 12: 1: 2: 3: And, the Horizon System cusps are: MC = 10: CAN 21°16.6' 11: 12: VTX = 1: 2: 3:

See also:

♦ Pseudo-house Circle ♦ Jayne, Charles ♦ Zenith ♦ House System ♦ Meridian ♦ House Cusp ♦ Prime Vertical ♦ Ecliptic ♦ Anti-vertex ♦ Vertex ♦ Great Circle ♦ Nadir ♦ Lune ♦ Mc ♦ Asc (Ascendant)

**Horizon House System**[Prima]

Also called the Zenith house system. This is a "pseudo" house system in which lunes (pseudo-houses) are formed by great circles that pass through the zenith and nadir -- rather than the north and south points along the horizon — starting at the meridian and progressing toward the eastern half of the prime vertical.

Each pseudo house is the same size; i.e. each lune is 30°. The MC is the 10th-house cusp, but the ASC is not the 1st-house cusp; instead, the intersection of the ecliptic with the eastern half of the prime vertical is used. This point is also known as the anti-vertex and is opposite the vertex or electrical ascendant. The American astrologer Charles Jayne advised serious investigation of the Zenith (Horizon) system, although he preferred the Campanus house system.

A Campanus Table of Houses may be used the compute the house cusps for the Horizon system: - add 12 hours to the given Sidereal Time; - determine the tabular values for the colatitude of the given place; - add 180° to the longitudes obtained.

See also:

♦ Pseudo-house Circle ♦ Jayne, Charles ♦ Zenith ♦ House System ♦ Meridian ♦ House Cusp ♦ Prime Vertical ♦ Ecliptic ♦ Anti-vertex ♦ Vertex ♦ Great Circle ♦ Nadir ♦ Lune ♦ Mc ♦ Asc (Ascendant)

**Horizon Parallax**[Astro*Index]

The angle subtended at the center of a body Moon [?] between the line connecting the centers of the Earth and Moon and a line tangent to the surface of the Earth. Horizontal Parallax is tabulated each 12 hours (0h and 12h) for the Moon, and each day for the Sun, in the AENA (American Ephemeris and Nautical Almanac). Horizontal Parallax for the Moon varies between 53'53" and 61'27"; for the Sun, between 8.65" and 8.96". The Equatorial Horizontal Parallax at mean distance for the Moon is 57'02.57", or 3422.57"; and, for the Sun is 8.798". Horizontal Parallax is an effective measure of the distance of the body from the Earth. — or, Also called the Horizontal Geocentric Parallax. The largest possible value of Geocentric Parallax. Its value is equal the size of the apparent semi-diameter of the Earth as observed from the body.

See also:

♦ Geocentric Parallax ♦ Parallax

**Horizon, Poles of the**[Astro*Index]

The observer's *Zenith* and *Nadir*, which are the intersections of the *local vertical* with the *Celestial Sphere*.

See also:

♦ Zenith ♦ Nadir ♦ Celestial Sphere

Astro*Index Copyright © 1997 Michael Erlewine

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