OPEN STAR CLUSTERS
M-11 (NGC-6705): An exceptional galactic open cluster, located in the constellation
of Scutum. This rich cluster contains 400 stars brighter than 14th magnitude. Its visual
size is approximately 12 minutes of arc, which at its accepted distance of 5500 light
years translates to a diameter of approximately 20 light years.
NOTE: This image was captured on 8/24/06, and is an integration of ten 30 second
exposures through the 80mm f/7.5 ED Apochromatic Refractor. The images were
combined and processed in Maxim DL Essentials, with additional post-processing in
Photoshop CS.
of Scutum. This rich cluster contains 400 stars brighter than 14th magnitude. Its visual
size is approximately 12 minutes of arc, which at its accepted distance of 5500 light
years translates to a diameter of approximately 20 light years.
NOTE: This image was captured on 8/24/06, and is an integration of ten 30 second
exposures through the 80mm f/7.5 ED Apochromatic Refractor. The images were
combined and processed in Maxim DL Essentials, with additional post-processing in
Photoshop CS.
(CLICK ON THUMBNAIL IMAGE FOR FULL-SIZE VIEW)
M-71 (NGC-6838): Located in the constellation Sagitta, approximately midway between
Delta and Gamma Sagittae. A rich and compact cluster of faint stars. Its visual size is
approximately 6 minutes of arc, which at its accepted distance of 18,000 light years
corresponds to a diameter of approximately 30 light years. M-71 is an unusual cluster
whose precise classification is somewhat in doubt. Harlow Shapley and R.J. Trumpler
both classified it as an open cluster, but in most modern publications it is listed as a
globular cluster. The H-R diagram shows a red giant sequence resembling that of a
globular cluster, but spectroscopy shows that the member stars are metal-rich, which
does not support classification as a globular.
NOTE: This image was captured on 8/24/06, and is an integration of fifteen 40 second
exposures through the 80mm f/7.5 ED Apochromatic Refractor. The images were
combined and processed in Maxim DL Essentials, with additional post-processing in
Photoshop CS.
Delta and Gamma Sagittae. A rich and compact cluster of faint stars. Its visual size is
approximately 6 minutes of arc, which at its accepted distance of 18,000 light years
corresponds to a diameter of approximately 30 light years. M-71 is an unusual cluster
whose precise classification is somewhat in doubt. Harlow Shapley and R.J. Trumpler
both classified it as an open cluster, but in most modern publications it is listed as a
globular cluster. The H-R diagram shows a red giant sequence resembling that of a
globular cluster, but spectroscopy shows that the member stars are metal-rich, which
does not support classification as a globular.
NOTE: This image was captured on 8/24/06, and is an integration of fifteen 40 second
exposures through the 80mm f/7.5 ED Apochromatic Refractor. The images were
combined and processed in Maxim DL Essentials, with additional post-processing in
Photoshop CS.
NGC-7789: Located in the constellation of Cassiopeia, between the stars Rho and Sigma
Cassiopeiae. A very rich galactic open star cluster. It contains almost 1,000 stars, and its
visual size is approximately 20 minutes of arc, which translates to an actual diameter of
about 50 light years, given its accepted distance of 6,000 light years. Spectroscopic
study reveals this cluster to be much older than most open clusters.
NOTE: This image was captured on 9/1/06, and is an integration of ten 90 second
exposures through the 80mm f/7.5 ED Apochromatic Refractor. The images were
combined and processed in Maxim DL Essentials, with additional post-processing in
Photoshop CS.
Cassiopeiae. A very rich galactic open star cluster. It contains almost 1,000 stars, and its
visual size is approximately 20 minutes of arc, which translates to an actual diameter of
about 50 light years, given its accepted distance of 6,000 light years. Spectroscopic
study reveals this cluster to be much older than most open clusters.
NOTE: This image was captured on 9/1/06, and is an integration of ten 90 second
exposures through the 80mm f/7.5 ED Apochromatic Refractor. The images were
combined and processed in Maxim DL Essentials, with additional post-processing in
Photoshop CS.
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M-46 (NGC-2437): Located in the constellation of Puppis, about 14 degrees east of the
brilliant star Sirius (Alpha Canis Majoris). Discovered by Charles Messier in 1771. It con-
tains about 200 stars ranging from 10th magnitude down to 14th magnitude and has a
visual size of approximately 25 minutes of arc. The brightest members are blue giants of
spectral class AO, each having a true luminosity of over 100 times that of the sun. This
cluster lies at a distance of about 5400 light years from earth. A curious feature of this
cluster is the presence of the small planetary nebula NGC-2438, located approximately
7 arcminutes north of the center of the cluster. It shows up in this CCD image just to the
lower left of the center of the frame. It is believed that the nebula is not actually a
member of M-46, as its radial velocity indicates that it is probably 3300 light years from
earth. This means that it is an "optical" or "line of sight" member of the cluster.
NOTE: This image was captured on the evening of January 25th, 2007, and is an
integration of thirty 20 second exposures through an 80mm f/7.5 ED Apochromatic
Refractor. The images were combined and processed in Maxim DL Essentials, with
additional post-processing in Photoshop CS.
brilliant star Sirius (Alpha Canis Majoris). Discovered by Charles Messier in 1771. It con-
tains about 200 stars ranging from 10th magnitude down to 14th magnitude and has a
visual size of approximately 25 minutes of arc. The brightest members are blue giants of
spectral class AO, each having a true luminosity of over 100 times that of the sun. This
cluster lies at a distance of about 5400 light years from earth. A curious feature of this
cluster is the presence of the small planetary nebula NGC-2438, located approximately
7 arcminutes north of the center of the cluster. It shows up in this CCD image just to the
lower left of the center of the frame. It is believed that the nebula is not actually a
member of M-46, as its radial velocity indicates that it is probably 3300 light years from
earth. This means that it is an "optical" or "line of sight" member of the cluster.
NOTE: This image was captured on the evening of January 25th, 2007, and is an
integration of thirty 20 second exposures through an 80mm f/7.5 ED Apochromatic
Refractor. The images were combined and processed in Maxim DL Essentials, with
additional post-processing in Photoshop CS.
