[AZ-Observing] Some Open Clusters in Orion
- From: Tom Polakis <tpolakis@xxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Mon, 19 Jan 2004 18:47:41
Lacking a good observing plan, I arrived at Vekol in the early evening
hours. I brought Archinal and Hynes' excellent book "Star Cluster" with
the hope that I'd come up with something. Orion was high, so open clusters
in Orion it was. I skipped some of the brightest clusters and the ones
given as infrared clusters, and took notes on the rest. I added a few
observations from Sentinel the next night.
Dolidze 21: As Skiff notes, it was not obvious. I did noticed a dozen or
so bright stars over a 10' diameter about 10' south-southwest of the
cluster's catalogued position, but I don't know if that's the cluster.
Berkeley 20: This one's catalogued as 2' across, but I only saw four stars
at the limit of my 10-inch scope (~15th magnitude) across a 30" diameter.
They surrounded an 11th-magnitude star.
Collinder 69: The Sigma Orionis cluster, listed as having 20 stars. I
can't honestly say that I saw a cluster here, but Sigma Ori sure is a
pretty multiple star! Sigma is flanked by equally bright stars separated
by 5". At the opposite diagonal of a long rectangle of bright stars is
another equal-magnitude double also separated by 5".
Collinder 74: It's an easy star-hop from Betelgeuse to this field, which is
listed as containing 40 stars in a 6' diameter. I saw 15 of them in a 4'
field with some background haze.
Berkeley 72: This one is at the northern extreme of the constellation. For
some reason, I enjoy looking at this type of cluster that's right at the
limit of my vision. I saw an extremely faint haze 2' across at 200x. In
that haze, I counted 8 stars that popped in and out of the clumpy region.
Berkely 21: Here's another extremely faint cluster that appears as no more
than clumpy haze. "Star Clusters" gives 194 stars and 6', but the 10-inch
showed zero stars and 2'. A chain of four equally spaced stars lies to the
east.
NGC 2141: That's more like it! Here is a prominent, bright haze 6' across
in a sparkling field. At 110x, the 10-inch showed 40 stars, but they are
very difficult to separate from the surroundings.
NGC 2180: In the 10-inch, I saw 30 stars ranging from 10th to 13th
magnitude across a 7' diameter. Skiff asks if a visaul observation may
better define its center, but this is not my forte'. I will say that the
center appeared to lie as much as 2' north of the listed position, which
lies almost on top of a magnitude 8 star.
NGC 2194: This is a very nicely defined cluster of 40 stars between 12th
and 14th magnitude, about 5' across. A stong background haze suggests that
there are more stars not showing up in my little scope.
Skiff J0614.8_1252: I decided to go after the neighboring cluster, and was
surprised to find it quite easily. In the same medium-power field are two
clumps of a dozen stars each that are 3' across, and separated by 3'. They
stand out very well in the field. I wonder how many times this group of
stars had been noticed before Brian determined that it was a cluster.
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