Astro*Dictionary by Michael Erlewine

9 articles for "Oblique"

Oblique Ascendant [DeVore]

v. Ascensional Difference.

Oblique Ascension (OA) [Astro*Index]

(OA)

If it exists, the Right Ascension of the point lying on the Celestial Equator which rises at the same moment as the given body. Its value may be computed from the RA (Right Ascension) of the body, and its AD (Ascensional Difference) — which depends upon the observer's latitude.

See also: ♦ Oblique Descension ♦ Right Ascension ♦ Celestial Equator ♦ Ascensional Difference
Oblique Ascension [Munkasey M.]

(1) That equivalent point of the CelestialEquator which rises with a body as the body rises across the Horizon.

(2) An arc of the Body as it travels on its rising path. OA is measured along the Celestial Equator from the Aries Point. OA (or OD) are used to direct (or, measure distance between') a body and the ASC (or Horizon).

See also: ♦ Oblique Descension ♦ Right Ascension ♦ Celestial Equator ♦ Ascensional Difference
Oblique Ascension [DeVore]

(O.A.) As it rises, a star or planet, not on the equator, forms an angle with that part of the equator which is rising at the same time. This is called its Ascensional difference. (A.D.) This A.D. added to the R.A. if it have S. declination, and subtracted therefrom if it have N. declination, gives its Oblique Ascension. In the Southern hemisphere, reverse; add, if N.; subtract, if S.

The equator is always at right angles to a line between the North and South Poles. Any meridian circle can be considered as the horizon of a place on the equator go degrees distant from that meridian — hence, from that point such meridian can be called the horizon of the pole.

At either pole a planet on any parallel of declination moves along an arc parallel to the equator, to the horizon of the pole. It has neither ascension nor descension, but remains, day and night, above or below the horizon, according as it is in North or South declination. Viewed from a place on the equator, a star will by the axial rotation of the Earth, be carried along an arc parallel to the equator: hence it rises and sets at right angles to the horizon of that place. All places in latitudes north and south of the equator, have a prime vertical that cuts the equator at an angle equal to the latitude of the place; and the horizon cuts the equator at an angle equal to the complement of the latitude. Stars and planets rise and set obliquely, since they follow arcs parallel to the equator — to which the horizon is oblique. The semi-arc of a body on the equator is always go degrees, or 6 hours; the whole arc is always 180 degrees or 12 hours. On the equator days and nights are equal, and the semi-arcs of all bodies are equal; but in latitudes north or south of the equator the arcs above and below the horizon are unequal, although together these make 180 degrees or 12 hours. The difference between 90 degrees and the diurnal or nocturnal semi-arc of a body is thus its Ascensional Difference; and its Right Ascension, plus or minus this Ascensional Difference, is its Oblique Ascension.

See also: ♦ Oblique Descension ♦ Right Ascension ♦ Celestial Equator ♦ Ascensional Difference
Oblique Descension (OD) [Astro*Index]

(OD)

If it exists, the Right Ascension of a point lying on the Celestial Equator which sets at the same moment as the body. Its value may be computed from the RA (Right Ascension) of the body, and its AD (Ascensional Difference) — which depends upon the observer's latitude.

See also: ♦ Oblique Ascension ♦ Right Ascension ♦ Celestial Equator ♦ Ascensional Difference
Oblique Descension [Munkasey M.]

Used in the same sense as "Oblique Ascension", but used with a body that is setting and not rising. OD is used to measure a body's position when it is West of the Meridian.

See also: ♦ Oblique Ascension ♦ Right Ascension ♦ Celestial Equator ♦ Ascensional Difference
Oblique Descension [DeVore]

(OD)

The complement of Oblique Ascension: 180 degrees, minus the Oblique Ascension, equals the Oblique Descension.

See also: ♦ Oblique Ascension ♦ Right Ascension ♦ Celestial Equator ♦ Ascensional Difference
Oblique Sphere [Astro*Index]

(OD)

An orientation of the Celestial Sphere for which the Celestial Poles are located elsewhere than at either the North and South points of the Horizon or the Zenith and Nadir points. This alignment occurs only for terrestrial locations other than along the Earth's equator, or at its north and south poles. Other orientations of the Celestial Sphere are called Right Sphere and Parallel Sphere.

See also: ♦ North Point ♦ Celestial Sphere ♦ Celestial Pole ♦ Zenith ♦ Nadir ♦ Right Sphere ♦ Parallel
Oblique Sphere [DeVore]

(OD)

Any sphere that is not in the same vertical as the poles of the Earth. All circles parallel to the equator arc oblique to the horizon — caused by the depression of the pole of the place from the Pole of the Earth. All places located between the poles and the equator are in an oblique sphere.

See also: ♦ North Point ♦ Celestial Sphere ♦ Celestial Pole ♦ Zenith ♦ Nadir ♦ Right Sphere ♦ Parallel