John Herschel discovered NGC 639 = h2430 (along with NGC 642 = h2431) on 27 Sep 1834 and noted "vF, vS; the preceding of two [with NGC 642].". His mean position from 3 observations matches ESO 413-013 = PGC 6105.

400/500mm - 17.5" (12/20/95): extremely faint, very small. Fainter of a close pair with NGC 642 1.7' NE. At first only a 10" round core seen, but with extended viewing can just detect faint extensions which increase dimensions to 0.9'x0.2' SW-NE.

Notes by Steve Gottlieb