NGC 752 -- Open Cluster in Andromeda
Old But Still Together
If you find yourself under truly dark skies and the Andromeda Galaxy (M31) is visible to the
unaided eye, try to see the nearby Open Cluster NGC 752 which is located about 4 degrees
below Alamak (Gamma Andromedae). If the sky is perfect, you will see NGC 752 as a soft
glowing-patch slightly larger than the full moon. I have seen it visually a couple of times, but
not at, or near, my house in Maryland. However, using binoculars from Alpha Ridge Park,
near my house, the cluster makes itself known as a few scattered stars covering a soft glow.
With my 110mm Refractor and lowest-power eyepiece, the resulting 3.4-degree field-of-view,
nicely frames the Open Cluster. She is a beautiful sight. Since NGC 752 is so large (75
arcminutes across) telescopes that do not provide wide enough views can fail to recognize
the cluster. Binoculars is the tool to use, unless you own a rich-field telescope, under
suburban skies.
NGC 752 is old for an open cluster. It’s mostly F-type subgiant stars are approximately
2 billion years old. Open Clusters tend to be short lived. Usually, the gravitational stresses
pull the cluster apart in tens of millions of years; sending their stars out on their own trajectories
[our own sun started its life in an open cluster that has long since fallen apart]. But a few clusters,
like NGC 752, seem to be able to keep themselves together for much longer.
unaided eye, try to see the nearby Open Cluster NGC 752 which is located about 4 degrees
below Alamak (Gamma Andromedae). If the sky is perfect, you will see NGC 752 as a soft
glowing-patch slightly larger than the full moon. I have seen it visually a couple of times, but
not at, or near, my house in Maryland. However, using binoculars from Alpha Ridge Park,
near my house, the cluster makes itself known as a few scattered stars covering a soft glow.
With my 110mm Refractor and lowest-power eyepiece, the resulting 3.4-degree field-of-view,
nicely frames the Open Cluster. She is a beautiful sight. Since NGC 752 is so large (75
arcminutes across) telescopes that do not provide wide enough views can fail to recognize
the cluster. Binoculars is the tool to use, unless you own a rich-field telescope, under
suburban skies.
NGC 752 is old for an open cluster. It’s mostly F-type subgiant stars are approximately
2 billion years old. Open Clusters tend to be short lived. Usually, the gravitational stresses
pull the cluster apart in tens of millions of years; sending their stars out on their own trajectories
[our own sun started its life in an open cluster that has long since fallen apart]. But a few clusters,
like NGC 752, seem to be able to keep themselves together for much longer.