Eleven prime NGC objects
A primer is a book or instructions providing help. A prime is a number divisible only by 1 and itself. The NGC contains 7,840 objects, and there are 990 prime numbers within that range. By far, most are galaxies. The fewest of any type — five — are planetary nebulae.
I have selected a prime number of these, 11, for your observing pleasure. (See “Eleven NGC objects,” below.) I picked the following objects because they are bright, interesting, and lie scattered across the heavens. They include clusters, nebulae, and galaxies.
NGC 281, discovered by American astronomer Edward Emerson Barnard five years before Dreyer published the NGC, is called the Pacman Nebula because a dust cloud gives it a “mouth” like the
video game icon. With a small telescope, under a sky free from light pollution, you’ll find it 1.7° east of magnitude 2.2 Alpha [α] Cassiopeiae.
NGC 457, a spectacular open cluster in Cassiopeia, was named the Owl Cluster in 1978 by Astronomy Editor David J. Eicher. This loose assemblage of stars includes a body, legs, open wings and two bright “eyes”(Phi1 and Phi2 Cassiopeiae), and is a wonderful sight in small telescopes.