Table 88. 

 MISCELLANEOUS ASTRONOMICAL DATA. 



109 



Length of sidereal year=365.2563578 mean solar days; 



= 365 days 6 hours 9 minutes 9.314 seconds. 



Length of tropical year=365.242i9987o — 0.0000062124 5? mean solar days; 



100 



=365 days 5 hours 48 minutes [46.069—0.53675 ^\ seconds. 



100 

 Length of sidereal month 



= 27.321661 162 — 0.00000026240 days : 



100 ■' ' 



= 27 days 7 hours 43 minutes ( 11-524 — 0.022671 — ) seconds. 



Length of synodical month 



= 29.530588435 — 0.00000030696 days ; 



= 29 days 12 hours 44 minutes / 2.841 — 0.026522 ^ seconds. 



Length of sidereal day =86164.09965 mean solar seconds. 



N- B. — The factor containing t in the above equations (the year at which the values of the 

 quantities are required) may in all ordinary cases be neglected. 



Mean distance from earth to sun ^92900000 miles = 149500000 kilometers. 

 Eccentricity of the earth 's orbit = e^ 



0.0 1 67 5 1 04 — 0.0000004180 (t — 1900) — 0.000000126 I — 1 



\ 100 j. 



Solar parallax = 8.7997"-!- 0.003 (Weinberg, A. N. 165, 1904) ; 



8.807 rt 0.0027 (Hinks, Eros, 7) ; 



8.799 (Samson, Jupiter satellites ; Harvard observations). 



Lunar parallax = 3422.68". 



Mean distance from earth to moon = 60.2669 terrestrial radii ; * 



= 238854 miles; 



= 384393 kilometers. 



Lunar inequality of the earth = Z = 6.454". 



Parallactic inequality of the moon = Q= 124.80". ■* 



, //— 1800 



Mean motion of moon's node in 365.25 days = ij. = — 19° 21' 19.6191" + 0.14136" — ioo~ 



Eccentricity and inclination of the moon's orbit = ^2 ^ 0.05490807. 

 Delaunay's 7 = sin | 7= 0.044886793. 



7= 5° 08' 43-3546". 

 Constant of nutation = 9.2'. 

 Constant of aberration =: 20.4962 -j- 0.006 (Weinberg, 1. c.).* 

 Time taken by light to traverse the mean radius of the earth's orbit 



= 498.82 J- o.i seconds (Weinberg) ; 

 = 498.64 (Samson). 

 Velocity of light = 186330 miles per second (Weinberg) ; 

 = 299870 -J- 0.03 kilometers per second. 

 General precession ^ 50.2564" + 0.000222 {t — 1900). 

 Obliquity of the ecliptic = 23° 27' 8.26" — 0.4684 (t — 1900). 



Gravitation constant =: 666.07 X lo-^o cm^/gr. sec^ -^ 0.16 X lO"!". 



* Recent work of Doolittle's and others indicates a value not less than 20.51. 

 Smithsonian Tables. 



