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What's up in the sky, July 2010

posted Jun 23, 2010, 11:30 AM by Marvin Stewart
           In the night sky now there are three constellations.  Each of the three have a bright star that is easily seen at dusk before the rest of the stars in those constellations appear. They have been dubbed the summer triangle. Vega, the bright star of the constellation Lyra, the lyre. Deneb, the bright star of Cygnus the Swan, and Altair, which is flanked on both sides by slightly dimmer stars in Aquilla, the Eagle. Anyone that has been interested in astronomy even a short time can find the trio, because they are that prominent.  And because they stand out, they are important navigation stars. They were important for those that traveled the caravan routes to China and sailors on long voyages. They were also known to the navigators in the Pacific who may have helped the Arabs to become excellent navigators too. 
          If it were possible to hang a plumb bob from the stars,  some would hang down and touch a city or a sea port you were trying to go to, or guide you back home. The bright star Vega passes over the City of St Louis. If you record the times Vega is directly over head where ever you are you will know when Vega is over St Louis. and how you must travel to get there. How can you tell a star is overhead? When I knew Vega was going to be overhead, I took a dark bowl partially filled with water and set it on the ground and for a few minutes. Vega was reflected off the water's surface in the bowl. I saw an old woodcut print of Arab traders doing this in the desert and  it works. The bowl may not be quite level on the ground but the water will be. If you know where the star is, and the time it will be there, you then will know where you are. Ancient travelers kept records and were able to develop tables of information to carry with them. By referring to those tables they could also use the stars to tell time as well as location.
        The bright star Deneb is further north than Vega. When Deneb first touches our Atlantic shore it passes over the Bay of Fundy, then moving west, runs along the international border between the State of New York and Canada, slightly on the Canadian side. The southern most star of the triangle, Altair, is high in the sky over Central America. Its declination of +08 degrees 52 minutes 06 seconds means it will pass over the Panama Canal.  Theta Aquila, usually shown as the wing tip star of the eagle, is to the left of and down from Altair.  That puts the eagle's wing tip slightly below Earth's equator. Altair and its two close companions, Beta and Gama Aquila, point to Theta Aquila like an arrow.  Beta and Gamma Aquila are also important navigational stars.
        7/ 03     Tonight the Moon will pass north of Jupiter at 8 P.M. CDT.
            04     Last quarter Moon.
            06     The Earth is at its furthest distance from the Sun ( aphelion )  94.5 million miles at 6 A.M. CDT.
            09     Venus just above the bright star Regulus 10 P.M. CDT
            11     New Moon.   A total solar eclipse in the South Pacific and South America.
       12-16    The waning crescent Moon will pass below four planets. 12th, Mercury, 14th Venus, !5th-16th Mars, the afternoon of the 16th Saturn.
            18     First quarter Moon.
            25     Full Moon.
            31    The Moon passes over Jupiter 4A.M. CDT.