Messier 3, also cataloged as NGC 5272, is one of the finest globular clusters for northern astrophotographers, glowing at magnitude 6.39 and spanning roughly 16′ across the sky. Its dense, symmetrical core surrounded by a rich halo of resolvable stars makes it a rewarding target that yields impressive detail even with modest apertures and moderate focal lengths. Because it packs enormous brightness into a compact form, careful exposure planning is essential to avoid burning out the concentrated center while still capturing the fainter outlying members. A moderate to long focal length paired with good seeing and precise focus will reveal thousands of pinpoint stars and the subtle color variations between them.
Names and Catalog numbers
- M 3 (Messier 3)
- NGC 5272
- Mel 119 (Melotte 119)
Position and the cosmic neighborhood
Messier 3 sits in Canes Venatici at a right ascension of 13h 42m and a declination of +28° 23′, placing it high in the spring skies of the northern hemisphere and well positioned for long imaging sessions. The surrounding star field is relatively sparse, which lets the cluster stand out cleanly against the dark background and simplifies framing and calibration. Its location roughly between the bright stars of Boötes and the Big Dipper’s handle makes it easy to locate for both visual star-hopping and plate-solved go-to setups. Lying about 32,600 light-years distant with a physical diameter of some 154 light-years, it is a distant but luminous island of stars that photographs beautifully as a standalone subject.
Nice to Know
- At magnitude 6.39, Messier 3 is bright enough to be spotted under dark skies with binoculars, yet it truly comes alive in long-exposure imaging.
- Its compact 16′ apparent size concentrates a wealth of stars, making it an ideal high-resolution target that rewards good seeing and accurate focus.
- The cluster is approaching us, with a radial velocity of -147.2 km/s, a value reflected in its slight blueshift of z = -0.000490886.
- Spanning about 154 light-years yet located some 32,600 light-years away, Messier 3 is one of the most star-rich globulars accessible to spring astrophotographers.
Brightness, distance and size
The object has an apparent magnitude of 6.4 mag, it lies about 32,600 light-years from Earth and spans roughly 154 light-years across. On the sky it appears about 16′ in size.
