M21 (NGC 6531) -- Open Cluster in Sagittarius
M21 is a small, quaint Open Cluster less than a degree from the Trifid Nebula.  To me it
appears like a double-star that has a short line of bright stars trailing behind and a faint
circle of stars above.  This cluster seems to have many hidden members that produce the
faint glow behind the 50 or so stars that make themselves visible in the telescope.  
Although this cluster is obvious and distinct from the background stars around it, the little
collection of stars just cannot compete with the nearby Trifid Nebula for shear splendor
and thus often only gets a casual glance by amateur astronomers.