|
This is the Christmas Tree Cluster, an open cluster with nebulosity which
includes the famous Cone Nebula. This cluster is located in Monoceros
and is about 2,400 light years distant.
The nebulosity is a nice combination of
reflection, emission and dark nebulosity and the dark nebulosity extends
well beyond the cluster itself in all directions and even beyond the top and
bottom of
the frame. Some knots of additional emission nebulosity can be seen
above the main cluster. The rich star field of the disk of the Milky Way behind
this cluster is eclipsed by the expansive cloud of dust and gas from which
the stars of the cluster were born.
The Cone Nebula, at the bottom of
the cluster is a part of the dark nebulosity of this object extending in
front of the emission nebulosity at the bottom of the cluster. It was
formed by radiation from the brighter stars at the top of the cluster
creating a pillar of dust and gas from which new stars are being born.
Protostars have formed at the tip of the cone.
The beautiful and dense star cluster on the right edge of the frame was a
pleasant surprise that showed up during the post processing. This is
Trumpler 5, a very old open star cluster that is massive enough to retain
its identity longer than normal for open clusters. The stars of open
clusters are loosely bound and tend to drift apart over time in an
accelerating process as the distance between stars increases. This
cluster is estimated to be about 125 million years old meaning most of the
truly massive stars of the cluster will have long ago gone supernova leaving
only the dimmer but very many stars of smaller size. In its early
days, this cluster would have been a truly spectacular, bright and dense
open cluster as seen from earth.
This is an experimental shot. On this night,
the conditions were a bit breezy and pushing the mount around some. So
I decided to shoot short exposures of one minute each but a lot of them to
see whether or not it's true that one can achieve the same results of depth
with many short exposures versus fewer longer exposures.
The total exposure time for this shot is 2 hours and, while the star fields
obviously show up well, the comparatively low surface brightness of the
nebulosity did not fare so well. My goal is to complete this experiment
by re-shooting this object with 40, 3 minute exposures for comparison.
I suspect that the nebulosity will be better captured with the longer
integrations even though the overall exposure is the same. I'll then
use exposures from both series to create a final image of the object.
This image has been stretched much more than is normally the case for images
from longer exposures. That excessive stretching has introduced other
artifacts that are obvious in the full size image.
Date: 2/25/2006
Location:
American Horse Lake
Telescope: Orion 80ED, f/7.5
Camera: Hutech Type I
350D, ISO 800
Calibration: 10, 60 second dark frames
average combined
Exposure Count: 120 @ 60 seconds
Guiding: ST-402ME, LX200GPS 10", CCDSoft
Post Processing:
Images Plus - Calibration, align and combine, digital
development
Neat Image - Noise reduction
Photoshop - Curves and levels
|
