NGC 7789 -- Open Cluster in Cassiopeia
Caroline Herschel, the sister to the famous astronomer Sir William Herschel, observed
for the first time, on October 18, 1787, the large, rich open-cluster NGC 7789. Caroline
was in her own-right a skilled observer and she “discovered” numerous deep-sky objects
while she scanned the heavens. The most accepted English name for this cluster is
Caroline’s Haystack. NGC 7789 ranks as one of her most impressive finds.
This dense open cluster contains over 580 stars ranging from magnitude 10 to 18
covering an area nearly as large as the full moon. In my 6-inch refractor the cluster is
dotted with visible stars set against a background of unresolved stars. The stars on the
edge of visibility fade in-and-out as I attempt to see details beyond the capability of my
telescope. A virtual haystack of stars upon stars.
This is a cluster that shows best when the field-of-view is one-degree or more. This
allows the thick star-cluster to be seen bordered by the interstellar space around it.
Pleasing in binoculars and stunning through the telescope this is a fine object to visit
when the Queen-of-Ethiopia (Cassiopeia) rides her throne high overhead.