NGC 6791 -- Open Cluster in Lyra
NGC 6791 (Old & Rich in Metals)
NGC 6791 is one of the oldest (some claim the oldest) and most metal-rich open clusters in
the Milky Way Galaxy. With an age of around 8 billion years and with the contents of its
stars containing higher than normal amounts of atoms heaver than helium (astronomer’s
definition of metals) it is unique among open clusters.
Only on the best of nights from my suburban home can I hope to find this cluster with my
155mm refractor. Each time I view it, I am struck by how much it resembles a faint globular
cluster just on the edge of being resolved. In the eyepiece the faint stars inside the ethereal
background glow fade in-and-out of existence. At a magnification of 137x, the cluster
teases the eye with its bewitching ephemeral background stars. At the magnification of
64x (used in the drawing) it settles down into a subtle soft smudge set against the milky way
star field. Both views are equally pleasing.