Messier 2 is probably the best globular cluster of the late-summer/early autumn sky, being a big and bright telescopic target that can also be swept up through 10 x 50 binoculars. It’s special too in that its individual stars are crammed together especially tightly.
How to observe:
Messier 2 (NGC 7089) shines at magnitude +6.4 and sports a healthy apparent diameter of 16’. These are impressive numbers, though Messier 2’s impact is tempered a little by its place within the southern constellation of Aquarius, the Water Bearer. Nevertheless, Messier 2 peaks in excess of a useful 35 degrees or so in altitude at about 10.20pm BST mid-month, owing to its location in the far northern reaches of Aquarius; sweep for a misty patch through binoculars on a transparent, moonless night five degrees north of third-magnitude Sadalsuud (beta [b] Aquarii).
Through a small telescope Messier 2 shows an unresolved sphere around 5’ across. It is rated as class II on the I–XII Shapley–Sawyer concentration class for globular clusters, making the resolution of its individual stars a particularly hard task for small- to medium-aperture telescopes. A 200mm (eight-inch) ‘scope at 200x will partially resolve M2’s more outlying stars, but it will need the resolving power of a 300mm (12-inch), working at high magnification, to pick out stars all the way to its core.
