3 From:	EXOS%"green@noao.edu" 30-DEC-1988 13:20:24.87  To:	JMS  CC:	 Subj:	 Phases of the Moon    Return-path: <green@noao.edu> D Received: from carina.noao.arizona.edu (noao.edu) by mis.arizona.edu6           id 20A000B8002 ; Wed, 28 Dec 88 00:27:49 MST% Received:  by noao.edu (5.59/SAG.G11) A 	id AA08699; Tue, 27 Dec 88 12:11:31 MST; for jms@mis.arizona.edu " Date:  Tue, 27 Dec 88 12:11:31 MST* Message-Id:  <8812271911.AA08699@noao.edu> To:  jms@mis.arizona.edu   Hello Joel Snyder,I    Your questions about the moon's phases are reasonable and interesting. H That "high point" is called "transit" by astronomers, and is achieved byJ every celestial object, including the moon.  It's a natural consequence ofJ their rising on the Eastern horizon and setting in the West; their highestJ apparent elevation in the sky (off the horizon) occurs halfway in between.L When the moon is full, it is exactly on the other side of the Earth from theK Sun.  Since the Sun transits at about noon, the full moon transits at about 	 midnight. K    Interestingly enough, the elevation of the moon's transit varies a great K deal throughout the year, and through each month (or lunation).  The moon's G orbital plane is tipped by about 29 degrees with respect to the Earth's O equatorial plane.  Each month, the moon describes a complete circuit, appearing K at +29 degrees to -29 degrees with respect to the Earth's equator projected M onto the sky.  The Earth "carries" the Moon and its orbit around the Sun with L it, so once a year the full Moon transits near the "top" of its orbit at +29M degrees (almost overhead in Tucson).  Six months later, the Moon will transit I very low in the sky, at about -29 degrees (28 degrees above the horizon). I While the full Moon transits at midnight each month, then, the height of  ( that transit varies from month to month.K    I'll be happy to provide an astronomy E-mail answering service.  Please   give my regards to Bruce. 0                                    Richard Green