Summer Triangle on the rise

Event Date: April 10th
Time: 5:00 AM


Brief

   Before dawn, a very large asterism can be seen looking east: The Summer Triangle.  Each star is part of a different constellation:  Vega in Lyra the Harp; Deneb in Cygnus the Swan; Altair in Aquila the Eagle.  All three stars are labeled in image one, while image two shows the constellation stick figures to go with them. Both images include the celestial grid, for reasoning mentioned in the detail section.

 

*click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

The only constellation figure that many people easily identify with its character is Cygnus, with the distinctive wingspan, head and tail.  Lyra contains an asterism within the entire triangle: a small parallelogram.  Aquila's brighter stars make up a large diamond.  Turning attention back to Cygnus, alot of people identify it as the northern cross-- to differentiate it that is, from the southern cross representing the small constellation Acrux not seen above our horizon.  This cross is too far south, and only the furthest southern U.S. latitudes see it clearly--albeit briefly--above the southern horizon. 
I will talk more about Acrux another day, while staying focused on the Summer triangle and its stars.

Detailed

   All three stars of the Summer triangle are north of the celestial equator.  I mention this, since as seen from most northern latitudes, they remain easily visible above the horizon most days of the year; either in the morning as it is this month, or in the evening during the summer, fall and early winter.  At far-enough north latitudes, Deneb and Vega are circumpolar, while Altair is only as such at very northern latitudes.  Since latitudes north of the arctic circle now have very little or no darkness at this time of year however, exact latitude depending, seeing Altair circumpolar means waiting until the late fall or early winter months.  Refer back to my Venus' apparition: mid and far-north latitudes entry a few days ago, as an example of the different paths that stars and planets take as seen from different latitudes on Earth.