M2

Its dense appearance is a useful contrast to the looser-looking M13. Both are globular clusters: old stellar systems whose visual texture changes markedly with observing conditions.

M2 is not a dependable Naked eye choice. Use a chart to learn Aquarius rather than expecting a clearly separate unaided patch.

Steady binoculars can distinguish a small hazy spot from the neighbouring stars under a sufficiently dark sky. They will not normally resolve the cluster into stars.

A small telescope shows the bright centre and diffuse outskirts. Medium aperture may reveal a grainy outer halo and a few resolved stars; larger aperture improves both detection of faint members and their separation. Try moderate power once located, then increase only if the halo remains visible.

Star-hop from the bright Aquarius pattern using a finder chart and confirm the glow stays in the same place when you move your gaze. Moonlight and light pollution preferentially remove the outer halo. Observe well above obstructions; low-altitude haze can leave only a misleadingly small core.

Use no nebula filter on M2. UHC, OIII and H-beta suppress stellar light rather than recovering the cluster members lost against a bright sky.

A smooth-looking core does not mean there are no stars there: unresolved members blend together. M2 contains multiple stellar populations studied with professional instruments; the eyepiece test is a much simpler distinction between haze, graininess and resolved points.