Eclipses and Other Phenomena: Transits and Occultations

Transit

• A transit occurs when a relatively small body passes across the disk of a larger body, usually the Sun or a planet, eclipsing only a very small area (Enclyclopedia Brittanica)
• Mercury and Venus will transit the sun, although very rarely
• A useful way to organize the Mercury's transits is by grouping them into series where each member is separated by 16,802 days or 46 years (= sum of 13 and 33 years).  Transits of Venus are much rarer; only six such events have occurred since the invention of the telescope (1631,1639, 1761,1769, 1874 and 1882) 

Occultation

• An occultation occurs when an apparently larger body passes in front of an apparently smaller one; usually describes the Moon passing in front of a star 
• A Total Solar Eclipse is effectively the same event as the Moon occulting the Sun

Sources: NASA; Encyclopedia Brittanica; Wikipedia