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11/24/2014 – Ephemeris – The Summer Triangle is still with us

November 24, 2014

Ephemeris for Monday, November 24th.  The sun will rise at 7:50.  It’ll be up for 9 hours and 16 minutes, setting at 5:07.   The moon, 2 days past new, will set at 7:29 this evening.

Well it’s almost Thanksgiving and about time that the Summer Triangle of bright summer stars finally set.  Except it won’t go just yet.  The stars Vega, Altair and Deneb are still hanging around in the west.  The bright summer part of the Milky Way is gone.  The constellations the three stars are in are Altair in Aquila the Eagle, now flying vertically up,  Deneb in Cygnus the swan flying vertically down, and Vega in Lyre the harp, lying on its side.  Altair the southernmost of these three will set first, later Vega will also set.  What happens to Deneb depends on your location in the Interlochen Public Radio area.  It you are north of Traverse City, Deneb will not actually set over Lake Michigan’s northern horizon.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.


Summer Triangle

The Summer Triangle at 9 p.m. on November 24, 2014. Created using Stellarium.

Vega Setting

Vega near its setting point at 11:07 p.m. p.m. on November 24, 2014. Created using Stellarium.

Deneb near setting?

Deneb near its setting point at 5:05 a.m. p.m. on November 25, 2014. Created using Stellarium.

But will Deneb really set for Traverse City.  Geometrically it will.  However with a flat northern horizon looking northward over the bays to a clean Lake Michigan horizon, atmospheric refraction will bend the light from Deneb making it appear higher in the sky than it really is, so it won’t actually set.  On the other side atmospheric extinction, the dimming of stars close to the horizon due to the filtering effect of looking through so much atmosphere would make Deneb impossible to see without a telescope.  It might be an interesting challenge to spot.

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