ASTR 207 Lecture Notes - Lecture 9: Solar Time, Analemma, Sidereal Time
21 Nov 2016
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Astronomical time periods: sidereal day - 23h56m07s. Earth completes one rotation on its axis: solar day - 24h. Sun makes one circuit around the sky: sidereal month - 27. 3 days. Moon completes one cycle of lunar phases (1/12 longer than a sidereal month: sidereal year - 365. 26 days. Earth completes one orbit around the sun: tropical year - 365. 24 days. Counted from one summer solstice to the next: planetary periods - can be measured relative to apparent position of. Sun (synodic) or relative to other stars (sidereal: transits - an inner planet aligns perfectly with sun during inferior conjunction, apparent solar time - given by position of sun in the local sky. Noon - when the sun crosses the meridian. Mean solar time - average duration of a day out of all the days in the year (used by clocks) Noon - average time in the day that the sun will cross the meridian.
