User:DraculavanHelsing/Books/History of Astronomy2 O-Z

O-Z

 * Observational astronomy
 * Occultation
 * Oort cloud
 * Opposition (planets)
 * Orbit
 * Orbital elements
 * Orbital inclination
 * Orbital mechanics
 * Orbital period
 * Orbital plane (astronomy)
 * Parsec
 * Percival Lowell
 * Phaeton (hypothetical planet)
 * Phases of Venus
 * Philosophiæ Naturalis Principia Mathematica
 * Planet Nine
 * Planet V
 * Planetary phase
 * Planets beyond Neptune
 * Poles of astronomical bodies
 * Precession
 * Primum Mobile
 * Proper motion
 * Ptolemy
 * Pythagorean astronomical system
 * Quadrature (astronomy)
 * Radial velocity
 * Retrograde and prograde motion
 * Richard A. Proctor
 * Roche limit
 * Rotation around a fixed axis
 * Rotation period
 * Rotational speed
 * Semi-major and semi-minor axes
 * Solstice
 * Spherical astronomy
 * Spherical Earth
 * Stellar parallax
 * Sublunary sphere
 * Theia (planet)
 * Themis (hypothetical moon)
 * Timeline of astronomy
 * Timeline of Solar System astronomy
 * Titius–Bode law
 * Transit (astronomy)
 * Triple conjunction
 * Turtles all the way down
 * Two-body problem
 * Tyche (hypothetical planet)
 * Tycho Brahe
 * Tychonic system
 * Urbain Le Verrier
 * Vulcan (hypothetical planet)
 * William Herschel
 * Zodiac