Open Cluster NGC 7789
Size: About 16'
RA: 23h 57m 0s
Dec: 56 degrees 43' 59"
NGC7789 was identified by Caroline
Herschel and is one of the oldest open star clusters known (about 1.6
billion years old). It sits in Cassiopeia amidst many stars of
the Milky Way galaxy, although the compact nature of this open cluster
makes it easy to identify. It contains at least 1000 stars of
varying ages, with several older, red giants being
easily visible. I
was not prepared for the sheer number of stars in this field, which
either add or detract from the beauty of the central star cluster,
depending upon your point of view.
Date: January 10, 2005
Sky 90 at f4.5 with field flattener/focal reducer, on the G11 Losmandy
Mount. I made a circular rim out of PVC tubing which fitted over
the dew shield of the Sky90 and permitted placement of an elastic band
to form an "X". This created the star spikes shown above for the
brighter stars. A photograph of this device is shown here (this
be accomplished with kite string or fishing line).
Autoguider: SBIG STV with
Type II R, G, B, plus clear filter set.
Exposures: L:R:G:B. 8 x 2'
for Luminance (clear filter); R, G, and B (5 x 3' each), all unbinned.
Conditions: Temperature 36 degrees F; average
transparency; average seeing; a bit breezy.
Post-processing: No darks,
flats, or bias frames used. Alignment and Min/Max Excluded
combine done in ImagesPlus.
performed in ImagesPlus
levels and curves adjustments in Photoshop CS (16 bit format).
note: Graphics on this website
may not be reproduced without author permission.
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