The Coma Star Cluster, Melotte 111, in Constellation Coma Berenices

Melotte 111, the Coma Star Cluster, is one of the largest and nearest open clusters visible from Earth. Spread across nearly 7.5 degrees of sky in the constellation Coma Berenices, this loose but physically bound group of roughly 40 bright stars is a rewarding wide-field target: capturing its full angular extent requires focal lengths well below 200mm.

General Data

Why Melotte 111 is attractive for astrophotography The cluster's extraordinary angular size makes it a natural target for fast telephoto lenses rather than traditional telescopes. At 135mm focal length on a full-frame sensor, Mel 111 fills roughly half the frame while the surrounding star field of Coma Berenices provides compositional context. The member stars — mostly A-type main-sequence dwarfs at magnitude 5–7 — are bright enough that even moderate total exposure times yield a striking image.

Situated at high galactic latitude (+88°), Melotte 111 lies virtually free of Milky Way dust and obscuration, providing a clean, dark background. This makes gradient correction more manageable than for clusters near the galactic plane. The speed of the Samyang 135mm f/2.8 lens further allows short individual sub-exposures while still accumulating substantial signal.

Observing Notes Melotte 111 reaches its highest altitude for mid-northern observers in late April and May, transiting near the zenith at declination +26°. It lies in the faint constellation Coma Berenices, roughly 6 degrees north of Denebola (β Leonis). Under a dark sky the cluster is immediately obvious to the naked eye as a loose sprinkling of stars; binoculars at low magnification give the most satisfying view, resolving the brightest members while preserving the full sense of scale. At 135mm, the entire cluster fits comfortably in a single frame, making framing straightforward.

Historical Context The group of stars known as Melotte 111 has been recognised since antiquity. Around 240 BCE the Egyptian astronomer Conon of Samos named these stars after Queen Berenice II of Egypt, who had cut her hair as an offering — giving rise to the constellation Coma Berenices. Tycho Brahe later listed the stars under Leo in his catalog rather than as a separate constellation. Philibert Jacques Melotte catalogued the group as entry 111 in his 1915 catalog of star clusters, and early proper-motion studies in the 20th century confirmed that the stars share a common space motion — establishing it as a genuine physical cluster at a distance of ~288 light-years.

Exposure Data:

• Lens: Samyang 135mm f/2.8

• Camera: Canon EOS 6Da, ISO 800

• Exposure Times

  • 116x60s

• Total: 1h 56min

• Date: 2026-04-11

• Location: Teide / Tenerife / Spain

• Mount: iOption Skyguider Pro

• Guiding and Exposure Control with INDI / PHD2 / CCDCiel running on XUbuntu Linux

• Image Processing PixInsight and Darktable

Sources:

• Wikipedia Article Coma Star Cluster (Melotte 111)

• Wikipedia Article Coma Berenices

• WEBDA Open Cluster Database – Melotte 111