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NGC 7789
Open Cluster
NGC 7789, OCL 269
Integrated Visual Magnitude: 7.5
Apparent Diameter: 15'
Distance: 6000 ly
Actual Diameter: 25 ly
Age: 1.7 Byr

Minimum requirements to view: binoculars and suburban skies


This is a large, beautiful open cluster that is visible as a hazy spot in binoculars.  Walter Scott Houston wrote that "NGC 7789 is one of those rare objects that is impressive in any size instrument."  He described the appearance in a 4-inch as "a soft glow nearly 1/2o across, and speckled with tiny, often illusive, individual stars."  The view in larger apertures is even more stunning.  I was impressed with how unusually round and regular this gathering appeared in my 18-inch and can only nod in agreement with Scotty's description of his view in a 16-inch, "the whole field is scattered with diamond dust."  William Herschel's sister Caroline discovered NGC 7789 in 1783.

Unlike the Double Cluster, this grouping of stars formed together relatively long ago for an open cluster, although the member stars are still relative newcomers, only about 2/5 as old as the earth and much, much younger than the globular clusters (which all formed around 11 billion years ago). 

 


NGC 7789 lies about 3o from Beta Cas.


The field in a 10-inch at 60x. North is down and east is to the right.

Millennium Star Atlas Vol III Chart 1083
Sky Atlas 2000 Chart 3
Uranometria 2000 Vol I Chart 59
.