12 articles for "Greenwich"

Civil Time for the Greenwich Meridian. Identical to Universal Time.

See also: ♦ Civil Time ♦ Universal Time

An angle, measured westward along the Celestial Equator, from the Greenwich Meridian to the Hour Circle passing through a body (planet or star). The angle may be expressed in degrees, minutes, and seconds (°'") or in hours, minutes, and seconds (hms). It may be calculated from the GST (Greenwich Sidereal Time) and the RA (Right Ascension) of the body using:       GHA = GST-RA.

See also: ♦ Celestial Equator ♦ Greenwich Meridian ♦ Hour Circle ♦ Greenwich Sidereal Time ♦ Right Ascension

(1) An arc measured in degrees along the Celestial Equator from the intersection point of the Prime Meridian.

(2) An arc measured in degrees alongthe Celestial Equator from the Greenwich Meridian to the Hour Circle of the Body.

See also: ♦ Celestial Equator ♦ Greenwich Meridian ♦ Hour Circle ♦ Greenwich Sidereal Time ♦ Right Ascension

The Greenwich Hour Angle of the Vernal Point. Equivalent to the GST (Greenwich Sidereal Time), but measured westward along the Celestial Equator. It may be calculated from the GST using:       GHA_Aries = 360°-GST.

See also: ♦ Vernal Point ♦ Greenwich Sidereal Time

An arc in degrees measured alongthe Celestial Equator from the Greenwich Meridian to the Aries point. This measurement is used in Celestial Navigation.

See also: ♦ Celestial Equator ♦ Vernal Point ♦ Greenwich Meridian

Greenwich Civil Time

See also: ♦ Greenwich Civil Time

Obsolete term. Used prior to 1925 to designate Mean Solar Time on the Greenwich Meridian. GMT has now been replaced by UT (Universal Time) throughout the scientific world. A few radio stations, and some astrologers, still use the older term, apparently unaware that they are actually using UT. GMT and UT are not identical in their measure of time, due to fundamental definitions. A similar change was made with LMT (Local Mean Time), which has been replaced with LCT (Local Civil Time).

See also: ♦ Mean Solar Time ♦ Greenwich Meridian ♦ Universal Time ♦ Local Mean Time ♦ Local Civil Time

The mean Solar time measured in reference tothe meridian of Greenwich, England.

See also: ♦ Mean Solar Time ♦ Greenwich Meridian ♦ Universal Time ♦ Local Mean Time ♦ Local Civil Time

Also called the Prime Meridian. The great circle on the Celestial Sphere that passes through the old Royal Observatory at Greenwich and the North and South Pole of the Earth's spin-axis. It is from this meridian that all longitude on Earth is measured. Also, Greenwich Civil Time and Universal Time are referred to this meridian.

See also: ♦ Prime Meridian ♦ Great Circle ♦ Celestial Sphere ♦ Greenwich Civil Time ♦ Universal Time

That terrestrial Meridian Circle which passesthrough Greenwich England's Royal Observatory, Herstmonceaux, and the North and South Poles of the Earth. It is from this Meridian that all Longitude (and also all clock time) is measured here on Earth.

See also: ♦ Prime Meridian ♦ Great Circle ♦ Celestial Sphere ♦ Greenwich Civil Time ♦ Universal Time

Sidereal Time on the Greenwich Meridian. The value is tabulated in the ephemeris under the heading Sidereal Time.

See also: ♦ Time ♦ Greenwich Meridian ♦ Sidereal Time ♦ Sidereal Time Calculation ♦ Greenwich Hour Angle

That Sidereal Time which is found in the daily entries of the various astrlogical ephemerides. It is also sometimes referred to as just simply "Sidereal Time".

See also: ♦ Time ♦ Greenwich Meridian ♦ Sidereal Time ♦ Sidereal Time Calculation ♦ Greenwich Hour Angle