The Pleiades (M45)

All Images Copyright Steve Cannistra

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Magnitude:  1.6
Distance: 380 light years
RA: 3h 46m 31s
Dec: 23 degrees 57' 36"

The Pleiades
(M45, the "Seven Sisters") convey a sense of stately, quiet winter beauty.  This open star cluster has been recognized since antiquity, with the oldest recorded observation being approximately 1000 years BC.  Within this cluster, it is possible to resolve between 7-11 stars with the naked eye, depending upon seeing conditions (and eyesight!).  Through the telescope, the cluster is known to contain about 500 stars that are gravitationally bound to each other.   The age of this cluster is estimated to be about 65 million years old, meaning that it was "born" around the time of the dinosaur extinction.  The beauty of this cluster is due to the impressive amount of blue nebulosity that appears to surround many of the stars (although is most likely not physically associated with the cluster).   During visual observation, there is a hint of nebulosity in a small scope such as an 8" SCT, although the full extent can only be observed in longer exposure photos such as this one.

Photographic Details:

Date:  Decmber 16, 2006
Scope:  FSQ-106 at f5, on the G11 Losmandy Mount.
Autoguider:  SBIG STV with e-finder.
Camera:  SBIG STL11000M, class 2 chip, -20C.

Astronomiks R, G, B filters (unmounted).
Exposures:  This is a BRGB image.  Red, 5' x 8; Green, 5' x 4; Blue 6' x 16, all unbinned.  Total exposure 156 minutes.
Conditions:  Temperature 38 degrees F, average transparency, average seeing, intermittent breeze, clouds invaded after 11 PM.
Post-processing:  Calibrated, aligned, and sigma clip combined in Maxim.  DDP in ImagesPlus (IP).  Further processing in Photoshop CS (16 bit format).  I did not have enough time to obtain a separate luminance channel before clouds rolled in.  Since the blue channel had good signal to noise, and I used it for luminance (with a mask to highlight only the central M45 region).

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