Last touched 2001 December 6
Originally published in M-111, the Newsletter of the Richland (Ohio) Astronomical Society
Reflections in the Eyepiece
As I walk out of the 31-inch dome, I wonder what I can look at next... the summer sky is all but gone and even the bright object autumn sky void is starting to slide into the western half of the sky.
M-31? No, it's too bright, and without a chart to show the details within the galaxy -- sounds like a good topic for the future -- it can be pretty boring.
M-76 is a good choice, and of course the double cluster is much too large to look at with the big blue beast. But I like galaxies.
NGC 891. This edge-on galaxy in Andromeda is always a crowd pleaser. It galaxy has a photographic magnitude of 10.8, so adding eight-tenths of a magnitude to magnitude 10 will give an approximate visual magnitude.
While most people know this galaxy as NGC 891, it also has the Uppsala General Catalogue (UGC) number of U1831. The UGC lists 891 as having a major axis of 14 minutes and a minor axis of three minutes in both red and blue light. UGC author Peter Nilson described 891 as a Hubble type SB galaxy with a inclination of seven, or almost completely edge on.
Located near Gamma Andromeda, the galaxy's major axis is positioned about 22 degrees from north. The big cigar shaped galaxy is a challenging object in a 6-inch telescope from moderate skies, while a 10-inch telescope in dark skies will show the galaxy's dark lane that splits the object into two pieces.
Since 891 has a pretty high surface brightness, it seems to take power very well. Smaller scopes will start to show detail like the dust lane at higher powers. Don't be afraid to try higher powers with this object.
In the 31-inch scope, I think 891 looks much better at 300x than 200x. The increase in detail at the higher power is worth the loss of brightness. A hood or jacket pulled over your head for a couple of minutes will allow your pupils to expand and increase your ability to pick out the faint detail.
In my beginning days of deep sky observing at Perkins Observatory in Delaware, Oh. in the early 1980's, I always looked at an incredible photograph of 891 that the observatory has hung on the lobby wall in a light box. This photograph shows an incredible wealth of detail to either side of the dust lane.
At 300x with the 31-inch scope, I can start to see this detail. Tiny twists and knots of gas and dust first show themselves as mottling that breaks into detail with a 16mm eyepiece in the 31-inch. At this power, the galaxy stretches across the entire field of view, and is a grand sight to behold. I always have an internal argument with myself as to if this galaxy is the best edge on or if NGC 4565 in Coma Bernices is the best of the bunch.
Another interesting thing about 891 is that it is hardly traveling away from the earth at the rate of 75 kilometer per second, meaning that it is pretty close to our Milky Way galaxy. Years ago, long before Dreyer's New General Catalogue, 891 was know as General Catalogue 527. Apparently, this galaxy was first noticed by William Herschel, and later observed by his son John.
While you are looking at NGC 891, be sure to bump the scope about five minutes east and a couple of minutes south. With you keep the 32mm eyepiece in the scope when you do this, you should start to see other faint galaxies in the area.
This is the region of Abell 347. This cluster of galaxies is not one of the richest of the Abell clusters with only 30 to 49 galaxies in it, but is one of the brightest -- with the photographic magnitude of the tenth brightest galaxy in the group is 13.3.
This cluster has nine NGC galaxies in it. These galaxies range in brightest from 13 to 15. All should be visible in the 31-inch or good 17.5-inch scopes from darker skies. The best resource for information about Abell 347 starts on page 120 of the fifth volume of the Webb Society's Deep Sky Observer's Handbook.
Even if you are not an observer of galaxy clusters, Abell 347 is a good object to look at. Unlike other galaxy clusters, Abell 347 is not so packed with individual objects as to make it almost impossible to figure out what is what. In the course of an hour, it is possible to identify and record a couple dozen objects.
So if you get a chance, enjoy the fall skies and look at some galaxies.
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