Messier 15 (NGC 7078) in Pegasus is a showpiece object of the early autumn sky and one of many best globular clusters to grace the northern sky. Globular clusters are a very spectacular class of deep-sky object, being densely-packed and near-spherical collections of historic stars.
Underneath a pristine darkish sky, eagle-eyed observers could spot it with the bare eye; by way of 10 x 50 binoculars it seems as a vivid, fuzzy ball. Messier 15 lies nicely above the celestial equator, so observers at mid-northern latitude gained’t face any low-altitude points. Certainly, its observable all through September at a good altitude from dusk by way of to close daybreak.
Tips on how to observe:
Messier 15 shines at magnitude +6.0 and spans 16’ to 18’ at its fullest extent (sources differ on M15’s obvious diameter). It’s situated 4 arcminutes north-west of magnitude +2.4 Enif (epsilon [ε] Pegasi), a place that from London sees it culminate shortly after 10.30pm BST at an altitude of round 50 levels.
A telescope within the 80mm (~three-inch) class reveals Messier 15 as a vivid unresolved haze some 4’ in obvious diameter. It’s a well-concentrated globular that’s rated IV on the I to XII focus scale. A 150mm (six-inch) telescope, working an influence of round 200x, intensifies the core’s look, although you’ll want the resolving energy of no less than a 200mm (eight-inch) ’scope to start to select the cluster’s outlying stars. On a gradual and clear night time, a 300mm (12-inch) telescope can resolve Messier 15 to its core.
Can you see planetary Pease 1?
Messier 15 is one among a small, choose group of globular clusters that may boast the presence of a planetary nebula amongst their teeming stars. Pease 1 was the primary planetary to be detected inside a globular cluster when, in 1927, American astronomer Francis Gladheim Pease noticed the nebula on a photographic plate taken with the 100-inch (~2.5-metre) Hooker Telescope at Mount Wilson Observatory in California, USA.
That object, in the present day generally known as Pease 1 and catalogued moreover as PK 65-27.1, shines faintly at magnitude +14.9 and lies simply 1.5’ north-east of Messier 15’s core. It reveals up nicely in one of the best novice pictures however is a troublesome visible problem, owing partly to its diminutive 3” obvious diameter and its place near Messier 15’s core, the place it’s embedded deeply amongst many stars of comparable brightness.
To have any probability of discovering it, a magnification of round 300x will must be delivered to bear on a really clear and nonetheless night time. If stars are twinkling fiercely overhead, neglect it! A 250–300mm (ten- to twelve-inch) telescope could also be ample to trace it down; when you’re certain that you simply’re trying in the correct place, slip an O-III filter into the sunshine practice.
