M26 is an 8th magnitude open cluster located in Scutum. It's positioned just a few degrees from the constellation's best known deep sky object, M11, the spectacular Wild Duck cluster. Although not nearly as impressive as its more illustrious neighbour, M26 is a nice compact grouping of stars when seen through telescopes.
Finding M26 is relatively easy once one is familiar with the faint stars that make up Scutum. First locate the brightest star in Aquila, Altair (α Aql - mag. +0.8). Positioned southwest of Altair is δ Aql (mag. +3.4). Imagine a line connecting Altair with δ Aql and then curve it southwards for about the same distance again until you reach a pair of 4th mag. stars, λ Aql and 12 Aql. Next extend a line from these two stars in a southwesterly direction for another 6 degrees to reach ε Sct (mag. +4.9) and δ Sct (mag. (v) +4.6 -> +4-8). M26 is located one degree southeast of δ Sct.
The cluster was discovered by Charles Messier on June 20, 1764. He described it as a cluster that needs a good instrument and contains no nebulosity.
M26 is not visible to the naked eye but can be spotted with binoculars. A pair of 10x50s shows the cluster as a noticeable slight compression in a rich Milky Way star field. Through a small telescope of 80mm (3.1-inch) aperture, M26 appears as a tight compact misty cluster, hinting on resolution, that covers about half the diameter of the full Moon.
The brightest stars in M26 are of 12th magnitude. Of these, about 25 are visible in 150-200mm (6-8 inch) scopes. Four of the brighter stars form a diamond shape near the centre of the cluster and averted vision reveals many more fainter stars. Overall there are about 90 members, many of which are resolvable in larger scopes.
M26 is about 5,000 light-years distant and is estimated to be 89 million years old. Its apparent size of 15 arc minutes corresponds to a spatial diameter of 22 light-years. An interesting feature of M26 is a region of low star density near the nucleus, most likely caused by an obscuring cloud of interstellar matter between us and the cluster.
Overall, M26 is an open cluster that's visible with binoculars and a nice telescopic object. It's best seen from June to September and although often overlooked because of nearby M11, it's well worth a view in its own right.
M26 Data Table
|Object Type||Open cluster|
|RA (J2000)||18h 45m 19s|
|DEC (J2000)||-09d 23m 01s|
|Apparent Size (arc mins)||15 x 15|
|Age (years)||89 Million|
|Number of Stars||90|
|Other Name||Collinder 389|