[AZ-Observing] M31 Globular Clusters from Cherry Road
- From: Tom Polakis <tpolakis@xxxxxxx>
- To: AZ-Observing@xxxxxxxxxxxxx
- Date: Mon, 6 Sep 2010 15:00:52 -0400
A group of us had a nice session last Saturday night at the Cherry Road site.
After M31 had gained enough altitude, I went after some of its globular
clusters with my 18-inch scope, typically using 275x.
The East Valley Astronomy Club has 25 of the brightest globular clusters in M31
( http://evaconline.org/m31globs.html ) as one of its observing programs, so I
worked from that list. A good "finder chart" is Rob Gendler's annotated image
of M31 ( http://www.robgendlerastropics.com/M31NMmosaicglobs.html ). And to
give you one more reference, probably the best set of notes is Steve Gottlieb's
notes for 37 M31 globulars (
http://astronomy-mall.com/Adventures.In.Deep.Space/gcm31.htm ).
I managed to observe eight globulars before my attention was diverted to
observing in a more neighborly fashion. It was enjoyable, and surprisingly easy
to determine the location of the globulars with Gendler's large-scale photo and
Megastar. Some of the globulars I went after have magnitudes in the mid-15's,
which made them a challenge to hold steady. I found a number of them to at
least appear "gray" compared to stars of similar magnitude. The background, be
it a dark lane or of the bright core of the galaxy, has a big effect on
visibility. I made my size estimates mostly from memory of the apparent size of
the disc of Jupiter's moon Ganymede, which is typically in the 1.5" to 2" range.
G1: This is the brightest of the globulars, and it's located fully 2 1/2
degrees away from the center of the Andromeda Galaxy. It is involved in a tiny
equilateral triangle with two comparison stars. I saw G1 as only 5" across at
most, with a bright core.
G33: This one is paired with a 15th-magnitude star less than 10" to the east.
G33 appears hazier than that star, and roughly as bright.
G35: I could just barely hold this one steady; it appeared very slightly
nebulous. Only 5' to the south I could see a strip of brightening of the field
that is the stellar association A122.
G52: Another faint one, due to placement against a bright background. In this
case, it's the edge of NGC 206, the galaxy's most prominent star cloud. It
appeared nearly 4" across.
G58: Close to the southern end of NGC 205. Faint, but easily held steady,
barely non-stellar with a bright center.
G78: As M31's globulars go, this one is bright and non-stellar, 5" in diameter.
It is seen against a brighter background. It's the acute corner of a 30-60
triangle with two 12th magnitude stars to the west.
G72: 5' north of G78. Faint, just barely non-stellar, as disc appears gray.
G64: Similar to G72 in brightness, may be showing a very small, uniform disc
during moments of good seeing.
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