NGC 6356 -- Globular Cluster in Ophiuchus
A Triangle of Globular Clusters – NGC 6356
Three Globular Clusters occur in a tight 3-degree triangle in the constellation Ophiuchus.
M9 and NGC 6356 are bright while the third NGC 6342 is much dimmer. As a rule, to
visit one, you might as well visit all three. None of the three show any real structure or are
resolved from my suburban house with the 6-inch refractor, but they make a nice triplet to
visit during a nice transparent sky. To me M9 and NGC 6356 are so close in brightness
and size to each other, it is a surprise that Messier only notice one of the clusters. It is sad
that he missed NGC 6356, which to me, is the most interesting of the two. Yes, M9 is a bit
brighter, but NGC 6356 is twice the distance from us and is so large that it ends-up
appearing as a close-equal to M9 in the night sky. The dim NGC 6342 is a challenge
under light-polluted skies and thus was a harder object to find. It took a bit of patience
and time, but I finally located its soft glow – not something I can always accomplish from
the deck of my house under less transparent skies.
M9 made Messier’s list, NGC 6356 made Stephen O’Meara’s Secret Deep list (#77) and
both NGC 6356 and NGC 6342 made the Herschel 400 list. But who listed them are not
important; their close location to each other makes them greater than their individual parts.