M2 on 11-11-2005
Done with my 17.5 inch scope and SBIG ST-7E CCD camera
Globular Cluster M2 (NGC 7089), class II, in Aquarius
M2 has a diameter of about 150 light-years, contains about 150,000 stars, and is "one of the richer and more compact globular clusters." (Burnham). This cluster is of notable ellipticity (ellipticity 9, or form E1). At about 36,000 light years it lies well beyond the Galactic Center.
Of its 21 known variables, most are of RR Lyrae type, with periods of about 16 to 19 days. But one variable is a RV Tauri star whose apparent magnitude varies between 12.5 and 14.0; this star has alternating deep and shallow minima, and was discovered in 1897 by the French amateur A. Chevremont.
Right Ascension21 : 33.5 (hours : minutes)
Declination-00 : 49 (degrees : minutes)
Distance 36,000 light-years
Visual Magnitude 6.3
Apparent Dimension 12.9 (arc minutes)