Constellation families are collections of constellations sharing some defining characteristic, such as proximity on the celestial sphere, common historical origin, or common mythological theme. In the Western tradition, most of the northern constellations stem from Ptolemy's list in the Almagest (which in turn has roots that go back to Mesopotamian astronomy), and most of the far southern constellations were introduced by sailors and astronomers who traveled to the south in the 16th to 18th centuries. Separate traditions arose in India and China. Menzel's families Donald H. Menzel, director of the Harvard Observatory, gathered several traditional groups in his popular account, A Field Guide to the Stars and Planets (1975), and adjusted and regularized them so that his handful of groups covered all 88 of the modern constellations. Of these families, one (Zodiac) straddles the ecliptic which divides the sky into north and south; one (Hercules) has nearly equal portions in the north and south; two are primarily in one hemisphere (Heavenly Waters in the south and Perseus in the north); and four are entirely in one hemisphere (La Caille, Bayer, and Orion in the south and Ursa Major in the north). Ursa Major Family The Ursa Major Family includes 10 northern constellations in the vicinity of Ursa Major: Ursa Major itself, Ursa Minor, Draco, Canes Venatici, Boötes, Coma Berenices, Corona Borealis, Camelopardalis, Lynx, and Leo Minor. The eponymous constellation Ursa Major contains the famous Big Dipper. Zodiac The Zodiac is a group of 12 constellations: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Sagittarius, Capricornus, Aquarius, Pisces. Some version of these constellations are found in traditions around the world, for this band around the celestial sphere includes the ecliptic, the apparent path of the sun through the year. These constellations therefore are all associated with zodiac signs. (The ecliptic also passes through the constellation Ophiuchus, which doesn't have an associated zodiac sign.) Perseus Family The Perseus Family includes several constellations associated with the Perseus myth: Cassiopeia, Cepheus, Andromeda, Perseus, Pegasus, and Cetus (representing the monster sent to devour Andromeda). Menzel also included a few neighboring constellations: Auriga, Lacerta, and Triangulum. Except for Cetus, these constellations all lie north of the ecliptic. The group reaches from near the north celestial pole to declination −30°. Hercules Family The Hercules Family is a group of constellations connected mainly by their adjacency on the celestial sphere. It is Menzel's largest grouping, and extends from