The Great Globular Cluster in Hercules (M13, NGC 6205)
Characteristics:
Magnitude: 7.0
Size: 0.36 degrees
Distance: 25,000 light years
RA: 16h 41m 38s
Dec: 36 degrees 28' 03"
Description:
No one forgets their first view of M13 in the eyepiece. It's a
remarkable site, with speckled stars arising from the center giving it
an almost 3-dimensional appearance. The above photograph
represents an approximately 1 degree FOV, which is enough to appreciate
M13 in the context of its neighbors like the galaxy NGC 6207 in the
upper right. This globular cluster is 25,000 light years away,
orbiting near the center of our galaxy. Globular clusters contain
stars at such high density that the night sky would be filled
with light, and planetary orbits would be unstable due to gravitational
influences
from nearby stars. Also, the stars of M13 are very old and
consequently
contain very little metal (they were formed at a time when basic
elements
like iron had not yet been forged by other stars). So it is
unlikely
that earthlike planets formed around any of the stars in this cluster.
The
message sent to M13 by the Arecibo Radio
Telescope team in 1974 will most likely fall on deaf ears.
Photographic
Details:
Date: September 2, 2004
Scope: Takahashi
Sky 90 at f4.5 with field flattener/focal reducer, on the G11 Losmandy
Mount.
Autoguider: SBIG STV with
e-finder.
Camera: SXV-H9
Filter: Astronomik
RGB type II filter set.
Exposures: RGB composite.
10 x 2' for R, G, and B each, binned
1 x 1, 60
minutes total.
Conditions: Temperature 55 degrees F; average
transparency; average seeing; calm.
Post-processing: No darks or
flats used. Two-star aligned
in ImagesPlus; Sigma combined using RC Sigma Reject in MaximDL,
followed by color combine and DDP
in ImagesPlus. Correction
of gradients in each channel using the background compensation tool in
ImagesPlus. Subsequent
levels and curves adjustments in Photoshop CS (16 bit format).
Please
note: Graphics on this website may not be reproduced without
author permission.
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