M92

From South Dublin Astronomical Society

M92
Type	Globular cluster
NGC	NGC 6341
Constellation	Hercules
Right Ascension	17h 17.1m
Declination	+43° 08'
Magnitude	6.5
Size	11 arc min.
Image:M92 messier image.jpg

Hercules hosts another Messier globular, M92, which languishes somewhat in observing backwaters because of it’s proximity to the more illustrious M13. It’s a little more distant too than M13 at 26,700 light-years and looks more condensed in binoculars – you might confuse it with a similarly bright star a little to the east if your instruments are not perfectly focussed. There’s a lovely scattering of many faint stars below the cluster in the same field that vague trace out a large southwest pointing arrowhead. To find M92, scan a little over one 5° binocular field-width north from Pi (π) Herculis, the star marking the top-left corner of the “Keystone” asterism. A piece of trivia is that the effect of precession of the Earth’s axis over a 25,800 year period causes the North Celestial Pole to pass within one degree of the cluster. Such was the case about 10,000 BC and this will next occur in 16,000 AD. A case of multiple (but very faint) Pole Star’s perhaps?