Charles Messier discovered M93 = NGC 2447 = h3098 on 20 Mar 1781. Caroline Herschel independently discovered the cluster on 26 Feb 1783 and recorded "Nebula, about 1 1/4 deg north preceding the bright star in the Ship [or more exactly] preceding the 1st Navis [Puppis] towards 23 Canis Majoris. My Brother examined it with [magnification] 460 and found not less than 20 stars, with 227 above 40. with a compound eyepiece perhaps 100 and 150 very beautiful, nothing nebulous among them. Messier has it not." Owen Gingerich determined that the reference to 1 (Rho) Navis, should read 7 (Zeta) Navis. Observing from the Cape of Good Hope, John Herschel noted "A fine cluster, scarcely scattered, pretty rich, not much more comp[ressed]. M [toward the middle]. Nearly fills field. Stars 8....13 m."

200/250mm - 8" (3/24/84): bright, very rich, triangular-shape, pretty compact, excellent field.

300/350mm - 13.1" (3/24/84): about 60 stars, bright, large, pretty rich. Contains a tight quadrilateral near the center with three faint companions.

400/500mm - 18" (3/2/08): very easy with any optical aid (at the threshold of naked-eye visibility) with a few of the brighter stars resolved in 15x50 IS binoculars. The cluster is fairly well resolved at 25x in the 80mm finder. The central region is superb in the 18" at 175x (13mm Ethos) with ~100 stars resolved in the 10' region and richest in the core. Appears fully resolved into mag 10-14 stars. A small, near parallelogram of 4 stars (sides ~40"x20") stands out near the center with numerous fainter stars nearby. The brightest star on the SW side of the cluster is a nice, unequal double (ARA 2066 = 8.3/11.3 at 10").

Notes by Steve Gottlieb