OPEN CLUSTERS by Al Lamperti, images by Frank Colosimo A Full Deck of Kings Open clusters can be pleasing to behold but tend to be elusive. Join the authors on their foray into the world of King open clusters. B right open clusters are quite dazzling to behold: Witness the Perseus Double Cluster. Part of their aesthetic beauty results from the high contrast between the brilliance of the stars and the inky-black background. Many open clusters are bright Messier or NGC objects. A wonderful introduction to the wide variety of open cluster designations, some off the beaten path, can be obtained by participating in the Astronomical League's Open Cluster Observing Program, complete with a downloadable manual (see https://is.gd/ALopencluster). However, as with technology, the aperture of telescopes and persistence of observers have increased over the years, and thus the discoveries of more challenging and perhaps lesser-known (and observed) open clusters have increased. Among the plethora of open cluster designations are those described by American astronomer Ivan King in two papers published in 1949 and 1965. There are 27 King open clusters that range from the obvious to perhaps a couple of bright stars with background haziness perceptible to the eye. Fourteen of the 27 King open clusters whimsically reside in "royal" constellations: Queen Cassiopeia and King Cepheus. (continued on page 64) 5′ q KING 9 Let's begin our foray into King open clusters by going to King 9 in Lacerta. Look for this cluster around 5′ northeast of NGC 7245. It's a small, nebulous object with only a handful of stars resolved. Mv* = 18 | S = 3′ | No. = 40 | Tr = I1m | Mag. = 272× p KING 10 Some stars seem to be resolved in this first cluster that we'll visit in Cepheus, but many are fainter and in the background. There's some milkiness to the cluster. Mv* = 11 | S = 4′ | No. = 40 | Tr = I1m | Mag. = 256× Cepheus and Lacerta 23h 30m 23h 00m 22h 30m 22h 00m +70° Star magnitudes King 11 k CEPHEUS +65° f 3 4 5 6 7 M52 King 10 King 20 b c King 18 +55° LACERTA CAS King 9 7245 ` 60 N OV E M B E R 2 019 * SK Y & TELESCOPE 5′ A LL IM AG ES BY FR A NK COLOSIM O King 19 +60°https://www.is.gd/ALopencluster