John Herschel discovered NGC 2138 = h2993 on 30 Nov 1834 and recorded "eF; S; R; has 3 B st pretty distinct towards the south." In 1926, Willem van den Bos described it visually as a "nebula; bM, 12 mag, 2 or 3 stars involved." (26-inch refractor, Union Observatory).

300/350mm - 14" (4/3/16 - Coonabarabran, 178x): relatively faint, small, round, 25"-30" diameter, slightly brighter core, low surface brightness, no resolution. Four bright field stars lie directly south including mag 7.9 HD 40624 2.9' SSE and mag 8.5 HD 40625 7.5' S, along with a mag 10 companion at ~45".

Notes by Steve Gottlieb