The Summer Triangle

   The month of August, while typically warm and humid offers an opportunity for using binoculars to observe several interesting groups of stars after sunset. One drawback is that local sunset is around 8:30 to 9 pm and then the sky doesn’t really darken for another hour or so meaning that stargazing may become more of a late night event. Despite this, looking more or less directly overhead near the zenith after local sunset are a trio of bright stars forming a familiar and distinctive asterism known as the ‘Summer Triangle‘. Centered along the Milky Way the triangle is formed by using a bright star from three different constellations. Deneb is from Cygnus the Swan, Vega is from Lyra the Harp, and Altair is from Aquila the Eagle.

Click on image to see full size

Click on image to see full size

   In the vicinity of the Summer Triangle are several open star clusters as well as three distinctive star patters both of which fit nicely within the field of view of binoculars. Two of these star patterns are small constellations – Delphinus the Dolphin, and Sagitta the Arrow, and the third one is the distinctive ‘Coathanger Cluster‘, or Brocchi’s Cluster in the small constellation of Vulpecula the Fox.
   Near the tail of Cygnus the Swan are two open star clusters that are within the reach of binoculars and low-magnification, wide-field eyepieces in a telescope. About 9 degrees from Deneb, the ‘tail’ of the swan, is the the open star cluster M39. This is a small loosely grouped cluster of about two dozen stars with a combined apparent magnitude of around 5. Approximately 7 degrees from Deneb in the opposite direction is another open star cluster, M29. Perhaps more easily found looking about 2 degrees from the star Sadr, M29 is a loose group of about 80 stars with a combined magnitude of 9, making this cluster a challenge for binoculars but easier with a telescope at low power.
   Much of the difficulty in seeing either of these two open star clusters comes from the glow of the Milky Way. But that in itself is not too bad as the Milky Way, especially along Cygnus, is a beautiful area to sweep across using binoculars.
   Click here to go to the Qué tal in the Current Skies web site for more observing information.

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