Friday, May 26, 2006

M106. What's the deal?

By all accounts M106 should be seen from our sidewalk observatory in Central Park. From all the guides I've read this member of the Canes Venatici I Galaxy cloud, along with M94 and M64, is one of the brighter galaxies in the sky. Nearby M63, a member of M51 Galaxy Group or potentially a member of M101 Galaxy Group, is another easy object to detect and observe. In the last two sessions, I tried for M106 with no success using the Tak FS102 refractor. Eyepieces used included Plossl 32mm with & without Barlow 2x and Nagler 7mm.

Tony Flanders writes of M106 "...for a pleasant change, is a resonably bright and obvious galaxy."
Flanders, a regular contributor to Sky and Telescope, gives a peak brightness value of 19.2 magnitudes per square arc-second (MSA).

The site linked here was presented in an abbreviated fashion in S&T a few years back. I still reference his work as the authoritative work on sub/urban observation. He covers the Messier catalog with some starhoppingtips and detailed descriptions. Using a variety of instruments in urban and suburban settings, he assigns an index value describing degree of difficulty and level of interest. Highly recommended for the novice and un-dark sky observer.

Roger Clark of Visual Astronomy of the Deep Sky fame, provides in his book a visual description of the magnitude 9.0, 20' x 6.5' galaxy, with a bright core measuring in at 8' x 3'. He goes on to mention that the surface brightness is 22.9 MSA. Clark describes the observation with an 8" to be "quite a surprise."

Brian Rachford assigns a value of 19.9 MSA for the inner 2' in his study of visual magnitudes, essentially the nucleus of the galaxy. While you're there check out this page which has a condensed list of galaxies that should be fairly easy for urban astronomers.

Lastly, I think Alan MacRobert offers his description in his book, Star-Hopping for Backyard Astronomers
, that he could even see it with cloudy skies!

Now when reading all of this M106 is easy. I have no doubt that I have the field after starhopping a short distance from 3 CVn. No galactic core or nucleus. What gives? Our skies under favorable conditions in a favorable direction can yield to object with a surface brightness of 20+ MSA, maybe as faint as 20.5 ~ 20.75 MSA.

I have seen M94 and M63 a few times with instruments as small as the Tak 22x60 bins to the Teleport 10". Yet M106 I cannot get in the smaller optics. I can't believe that I have to resort to the 10" to bag it and observe it. Either I am missing the field (which I doubt) or missing some of the description between the lines.