transit was not known until after it had happened, when the orbit was calculated, and although some observers later claimed to have seen the comet transiting the Sun at the time, these observations seem dubious. Transits of the moon It is theoretically possible for minor planets on an Earth-crossing orbit could transit the Moon. However, such events would be extremely rare since only a few catalogued minor planets, such as 2004 FH, have come closer to Earth than the distance of the Moon. Such an event might be observable (an asteroid of 25 metres' diameter at a distance of 380,000 km has an angular diameter of 0.01″), but none has been observed as yet, although there have been some reports of such events, sometimes classified as UFO-sightings. See also Transit of Mercury Transit of Venus Great Comet of 1819 References Martin Hoffmann, Asteroid transits over the disk of the Sun, Minor Planet Bulletin 16 (1989), 16 (1989MPBu...16...11H) External links JPL Horizons (useful for calculating positions of solar system objects) TRANSIT OF VENUS 2012: Live Webcast(Multipoint)- by SWAN-India Astronomical transits