Among all the wonderful nebulae that Cygnus has to offer are Messier 29 and 39, two beautiful open clusters that are easily visible with a pair of binoculars against a wonderful backdrop of the Milky Way as they rise on late summer evenings.
The bright summer constellation of Cygnus, the Swan, takes pride of place on late August and September evenings. Its familiar “Northern Cross” asterism of its brightest stars, led by the impressive first-magnitude Deneb (alpha (α) Cygni), is visible overhead as soon as true astronomical darkness sets in.
Due to its position embedded in the center of the summer Milky Way, Cygnus naturally hosts many open clusters, including Messier 29 (NGC 6913) and Messier 39 (NGC 7092).
Let’s start with the latter, M39, which to most observers is the superior cluster; it is certainly the larger and brighter of the pair, with its 30 main members shining with an integrated magnitude of +4.6 across 32 arcminutes the size of a full Moon. Its appearance is somewhat deceptive, as M39 is physically one of the closest of the Messier clusters (at 800 to 1,000 light-years away) and the smallest, with its member stars spread across just nine light-years of space.
Messier 39 is just visible to the naked eye as a bright dot against the rich background of the Milky Way, and lies about nine degrees northeast of Deneb and just under three degrees north of rho (ρ) Cygni. A small telescope at low power will show about 30 stars in a distinct triangular shape, but perhaps the best views are obtained with large binoculars.
Messier 29 is easy to spot with a pair of 10×50 binoculars as a tight knot of stars lying just under two degrees south-southeast of magnitude +2.2 Sadr (gamma (γ) Cygni). It shines with an integrated magnitude of +6.6 from its estimated composition of more than 200 stars and spans just seven arcminutes across the sky. A small telescope resolves its brightest stars into a pattern that gives it the appearance of a “mini Pleiades” lying in a rich field of the Milky Way.
Unfortunately, dust and interstellar gas along its line of sight severely damage it, reducing its brightness by more than three magnitudes.
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