local mean time


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Related to local mean time: UTC, Local apparent time

local mean time

[′lō·kəl ¦mēn ¦tīm]
(astronomy)
The arc of the celestial equator, or the angle at the celestial pole, between the lower branch of the local celestial meridian and the hour circle of the mean sun, measured westward from the lower branch of the local celestial meridian through 24 hours.

Local Mean Time

(religion, spiritualism, and occult)

Before the advent of rapid travel and modern means of long distance communication, particular localities kept time according to the noontime position of the Sun. Because this varied east or west of any given location, the local time also varied as one traveled east or west. The imposition of standard time zones, in which one must set her or his watch forward or backward as an imaginary line is crossed, is a comparatively recent innovation. Time zones serve many purposes, but, to properly cast a horoscope, astrologers must find the true local time during which a native was born. In other words, they must convert a birth time expressed in standard time back into local “Sun time.” The more common designation for Sun time is local mean time.

Traditionally, astrologers made this conversion by making certain calculations based on the longitude where a native was born. In more recent years, tables of time conversion (astrologers’ atlases, such as Longitudes and Latitudes in the U. S.) have been published by people who have made the necessary calculations for most large and medium-size cities, thus saving the astrologer a step in the calculations necessary to set up a chart. The personal computer revolution has largely eliminated the need for such tables, as such calculations have been incorporated into chart-casting programs.

Sources:

Dernay, Eugene. Longitudes and Latitudes in the U.S. Washington, DC: American Federation of Astrologers, 1945.
DeVore, Nicholas. Encyclopedia of Astrology. New York: Philosophical Library, 1947.
Filbey, John, and Peter Filbey. The Astrologer’s Companion. Wellingborough, Northamptonshire, UK: Aquarian Press, 1986.

local mean time (LMT)

local mean time (LMT)click for a larger image
The equatorial arc between the observer's antimeridian and the meridian of the mean sun measured westward and expressed in time, where 15.04° = 1 h (i.e., the time interval that has elapsed since the mean sun's transit of the observer's antimeridian).