Friday, September 16, 2011

The September Sky

.....This blog has not been updated in an uncharacteristically long stretch because of personal pressures with the beginning of a new school year, and my move to a new house, with an actual backyard - a backyard that has a line-of-sight to zero streetlights, instead of the eight at the apartment!  I hope that I don't become what I criticized (in backyard astronomers who assume everyone has good skies) now that my situation has improved!  (I am am in the city proper, though not a bright part of not a big city.)

.....Halfway through the month, here are the stars for September.  As is usual for this first pass, the constellation covered are in blue, tending to the west, while up-and-coming constellations have the eastern sky in red.

.....The limiting magnitude for this map is fourth magnitude, which could still be fairly optimistic for a lot of suburban and urban viewing.  When I did this, I also had to redraw a number of constellation patterns, as there are some constellations arranged in ways to make the figure hopefully look weakly, vaguely, as their namesakes, but squeezing this in often used faint stars that are hard to see under bright skies.

....Ursa Minor, the Little Dipper, is high on this list.  Only three of the seven stars can reliably be seen, so many, many people looking for the North Star by using the Little Dipper identify something else.  Pisces, wrapped around Pegasus, is another faint constellation with only a few bright stars.  If we overlay this map onto stars down to the limit of visibility, we find the patterns our backyard astronomy books promise us, but buried in an embarrassment of riches.

.....Locating constellations in September should start with the Summer Triangle.  The Triangle is at its zenith, the highest point in the sky,connecting the brightest stars in Aquila, Lyra, and Cygnus.  Rising in the East is the Great Square of Pegasus, a dimmer figure in a dimmer part of the sky.  You will be well rewarding for wandering out into the summer sky: the nights are cool enough to keep down the humidity (and hopefully the mosquitoes), and the last views of the summer Milky Way are visible in the southwest, the Milky Way itself passes directly above us.  Good Luck!