Astronomy: General

A Dictionary of Astronomy The Columbia Encyclopedia, 6th ed. Further reading

equation of time

A Dictionary of Astronomy | 1997 | Copyright

equation of time The difference between apparent solar time and mean solar time; technically, the difference between the hour angle of the true Sun and that of the fictitious mean sun. Whereas the mean sun by definition proceeds uniformly, the true Sun may be some minutes ahead of or behind its expected position because of the eccentricity of the Earth's orbit. Moreover, the true Sun moves along the ecliptic, not the celestial equator, which is an additional contributor to the equation of time. The difference reaches a maximum in early November, when apparent solar time is over 16 min ahead of mean solar time, and in mid-February, when apparent solar time is over 14 min behind mean solar time. The equation of time is zero on four occasions during the year: on April15, June14, September1, and December25.

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equation of time

The Columbia Encyclopedia, 6th ed. | 2011 | Copyright

equation of time see solar time .

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"equation of time." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1E1-X-equatn-t.html

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