M28

Globular cluster Messier 28 is in the constellation Sagittarius, at visual magnitude 6.8, just Northwest of Kaus Borealis. Lying at about 18,500 light years distance, M28 with its linear diameter of 60 light years appears considerably smaller and more compressed than its more impressive neighbor, M22. It is slightly elliptical shaped and requires larger instuments to resolve it into stars. The cluster lies in a particularly dense part of the Milky Way and thus is surrounded by numerous stars, giving the impression that M28 is actually much larger than it is in the sky. It contains 18 known RR Lyrae variables, a W Virginis variable with a period of 17 days, and a second long period variable, possibly of RV Tauri type, according to Burnham. M28 was the second globular clusters where a millisecond pulsar was discovered, in 1987. This one, 1620-26, is spinning around its axis once every 11 milliseconds.

Image taken Sept. 8, 2012, with the C-14 operating at F:7 and the ST-8 camera binnec 2 X 2. Exposure is 5 minutes, using Track and Accumulate.