M72 (NGC 6981) Observing Guide — Globular Cluster in Aquarius

Overview

M72 is a globular cluster in Aquarius, catalogued as NGC 6981. Shining at magnitude 9.3 and located about 55,000 light-years away, it is one of the fainter and more distant globular clusters in Messier's catalog — a genuine test of aperture and sky quality for observers tackling it on autumn nights.

Globular clusters are ancient, gravitationally bound systems of hundreds of thousands of stars, orbiting the Milky Way's outer halo. M72's distance puts it well beyond the Milky Way's central bulge, making it one of the more remote examples accessible to amateur instruments.

Basic Data

Physical Characteristics

M72 lies about 55,000 light-years from Earth and glows at magnitude 9.3. It is loosely concentrated compared to summer globulars like M80 or M92, which makes it more diffuse in appearance. Old red giant stars dominate its population, with an estimated age exceeding 10 billion years.

Observing Guide

Finding It

M72 sits in Aquarius and transits around 8–10 PM in autumn. Epsilon Aquarii provides a useful starting point — M72 lies about 3 degrees to its south-southeast. A nearby marker is M73, just over a degree to the east, which can be used as a stepping stone once you're in the right area.

Observing Tips

M72's lower concentration and distance make it appear more subdued than summer globulars. Use the contrast between its denser center and scattered outer stars to confirm identification. Averted vision helps the outer halo stand out against the dark sky. Good Seeing aids resolution at the cluster periphery.

Recommended Equipment

A medium telescope with at least 80mm aperture is needed to show M72 clearly. At 150mm or more under dark skies, some stellar resolution begins at the outer edges. This is not a target for suburban backyards — a site with minimal Light pollution is genuinely important here.

Astrophotography Tips

A tracking mount and camera on the telescope, with stacked exposures, captures M72 cleanly. Keep the exposure conservative on individual frames to retain core detail, then layer many sub-exposures during post-processing to draw out the outer halo.

Summary

M72 is an advanced autumn globular cluster that demands dark skies and a medium aperture to appreciate fully. Its distance and loose concentration make it a subtler target than the brilliant summer globulars, but completing the Messier catalog means getting to know M72 — and nearby M73 makes a convenient pairing in the same area of Aquarius.