DECIMAL CLASSIFICATION 
520 
Astronomy 
520.1 Astrology, see 133.5 520.2 Compends 520.3 Dictionaries 520.4 Essay® 
320.5 Periodicals 520.6 Societies 520.7 Study and teaching of astronomy 
520.8 Collections, etc. 520.9 History of astronomy 
See also note under Pure science in general, 500-509 
Theoretic astronomy 
Mathematic investigation of celestial motions, specially of the Solar system 
Motions of individual bodies ar clast under separate heds in 523 
Celestial dynamics 
General laws of equilibrium and motion 
Law of universal gravitation and motion 
See also 531.51 
Problem of 3 bodies 
Figures of hevenly bodies : 
Rotation of hevenly bodies 
Geocentric and heliocentric place 
Plane of orbit in space 
Position of orbit in its plane 
Position of body in its orbit 
Position of body in space 
Heliocentric longitude and latitude 
Geocentric longitude and latitude 
Variations of right ascension and declination 
Variations of longitude and latitude 
521 
AL 
II 
12 
13 
14 
IE 
2 
21 
22 
23 
24 
25 
26 
27 
28 
20 
Orbits 
Definitions of orbits 
Determination from 3 observations 
Determination from 4 observations 
Variation of elements of orbit 
Correction of approximate elements of orbit 
Application of method of least squares 
Kepler's problem 
Eauation of center and radius vector 
{ 
rn 
23 
il 
23 
20 
4 
Perturbations 
Mutual action of planets 
Action of satellites 
Nonsphericity of planets 
Resisting medium 
Theory of planets 
Theory of satellites 
Theory of comets 
Theory of eclipses 
Precession and nutation See also 522.95-.96 
41 
42 
43 
44 
5 
6 
7 
Q 
nN