[AZ-Observing] Extragalactic Globular Clusters from A Low Desert Site
- From: Tom Polakis <tpolakis@xxxxxxx>
- To: AZ-Observing@xxxxxxxxxxxxx
- Date: Mon, 3 Oct 2011 0:08:39 -0400
It has been a while since I took on some very difficult objects, so I put
together a list of globular clusters outside of the Milky Way. I have observed
about a dozen in the Andromeda Galaxy, and many of these are downright easy to
see with my 18-inch at a dark site. My list contained only the brightest one
or two globulars in other nearby galaxies. For each of them, I put together
finder charts from the Digitized Sky Survey. Looking at the magnitudes in the
16's and 17's, it was apparent that globular clusters beyond M31 were going to
be challenging targets.
The following observations were made with my 18-inch from a peaceful, quiet,
low desert site that is 45 miles due south of downtown Phoenix,. Conditions
were acceptable, with the Gegenschein apparent, but I could have used some more
distance from the big city.
NGC 205 (M110) is a bright companion to M31. Its brightest globular is Hubble
II, at magnitude V=16.7. I found it very difficult, but non-stellar. It
appeared at 270x as a haze about 3" across. It is conveniently pointed to by
two bright stars to the west-southwest.
Moving about 8 degrees to the north of M31 are the associated dwarf galaxies
NGC 147 and NGC 185. Both galaxies contain globular clusters. NGC 185
contains a magnitude 16.7 globular named FJJ V that I was able to see at 270x
about half of the time. Again, it appeared non-stellar compared to field
stars. It is involved in an equilateral triangle with two 14th-magnitude stars
to the north. I tried for Hodge II in NGC 147, but it was out of reach on this
night.
M33, the real Pinwheel Galaxy, was next. The cluster known as C39 is magnitude
15.9, and was easily held at lower magnifications. It's a long reach, but a
tight pair of two bright stars to the southeast point at the globular cluster.
The brightest globular in the faint Local Group galaxy Wolf-Lundmark-Melotte
(PGC 143) is magnitude 16.1, but I found it to be a bit of challenge until I
went to 380x to see it. A star just to the north is about one magnitude
brighter.
NGC 6822 (Barnard's Galaxy) contains several 'bright' globulars, but here the
problem that they are superposed on brightest region of the galaxy. Cluster H
VII is listed at magnitude 15.9, but it was difficult to hold steady at 380x.
The real motivation for doing this project was to try the observing stunt of
seeing a globular cluster in a galaxy outside the Local Group. In the Sculptor
Group are the large spiral galaxies NGC 253 and NGC 55, which contain many
globulars. I was unable to see either Globular #35 in NGC 253 or #43 in NGC
55. They are listed at magnitude 16.8 and 16.3, respectively, but they just
don't get high enough from my latitude. Put it in on the list for the next
trip to Chile.
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