mean sun

noun

a theoretical sun that moves along the celestial equator at a constant speed and completes its annual course in the same amount of time the real sun takes at variable speeds

• Hypernyms: ↑model, ↑theoretical account, ↑framework

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noun

Etymology: mean (VII)

: a fictitious sun supposed to move uniformly along the celestial equator completing crossings of the vernal equinox at intervals of a tropical year

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Astron.

an imaginary sun moving uniformly in the celestial equator and taking the same time to make its annual circuit as the true sun does in the ecliptic.

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mean sun noun

An imaginary sun moving uniformly in the equator, its position giving mean time or mean solar time (coinciding with true sun time four times a year)

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Main Entry: ↑mean

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mean sun,

a hypothetical sun in various astronomical calculations that moves uniformly along the celestial equator at the mean speed with which the real sun apparently moves along the ecliptic.

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n. an imaginary sun conceived as moving through the sky throughout the year at a constant speed equal to the mean rate of the real sun, used in calculating mean solar time