CHAPTER XXXII. TIME. 303. Interconversion of Time.-Sidereal time is referred to a fixed star, mean time to the sun. There is one more sidereal than solar day in the year. 366.24 sidereal days 365.24 mean solar days. 24 hrs. sidereal time = 23 hrs. 56 min. 04.091 sec. mean solar time. 24 hrs. mean time = 24 hrs. 03 min. 56.555 sec. sidereal time. and Relations of Sidereal, Civil, and Mean Solar Time. Ta, I when T, > a,;. 24"+ T, -- α, = I when T, < a,; a, (116) (117) T= T 12h for D, + I if Tm > 12h.. m t For example see Article 315. Relation of Sidereal Time to Right Ascension and Relations of Sidereal and Mean Solar Intervals of Time. -Letr ratio of tropical year, expressed in sidereal day to tropical year expressed in mean solar day; then INTERCONVERSION OF TIME. TABLE LV. CONVERSION OF SIDEREAL TIME INTO MEAN TIME. (From Smithsonian Geographical Tables.) 697 I' = rl = I + (r− 1)I = I + 0.0027381; (125) I = r−'I' = I' − (1 − r−1)I' = I' -0.0027301'. (126) These conversions are made by means of Tables LIV and LV, in which examples are shown. 304. Interconversion of Time and Arc.—In the performance of geodetic operations it frequently becomes necessary to convert time into longitude expressed in degrees of arc, and vice versa. The following tables facilitate this and similar operations and are for the interconversion of sidereal time and parts of the equator in degrees of arc, or of sidereal time and terrestrial longitude in arc. |