M22

Contributed by Denis Marquis from Québec, Canada

One of the most spectacular objects in Sagittarius is globular cluster M22. This easy naked-eye object ranks as the sky’s third-brightest globular, exceeded only by Omega Centauri (NGC 5139) and 47 Tucanae (NGC 104). In the Cycle of Celestial Objects, Admiral Smyth describes M22 as “A fine globular cluster, outlying that astral stream, the Via Lactea, in the space between the Archer’s head and bow, not far from the point of the winter solstice, and midway between m and s Sagittarii. It consists of very minute and thickly condensed particles of light, with a group of small stars preceding by 3', somewhat in a crucial form. Halley ascribes the discovery of this in 1665, to Abraham Ihle, the German; but it has been thought this name should have been Abraham Hill, who was one of the first council of the Royal Society, and was wont to dabble with astronomy. Hevelius, however, appears to have noticed it previous to 1665, so that neither Ihle nor Hill can be supported.” The cluster shines at magnitude 5.1. (4.4-inch Orion 110ED apochromatic refractor at f/7, Canon 1000D DSLR, ISO 800, thirteen 4-minute images, stacked)