William Herschel discovered NGC 1638 = H II-525 on 1 Feb 1786 (sweep 518) and described as "F, pL, lE." His position is 2' NW of the center of UGC 3133 = PGC 15824. The NGC position (from d'Arrest) is accurate. RNGC has an obvious typo in the RA (0h 01.3m)

300/350mm - 13" (12/18/82): fairly faint, fairly small, elongated 3:2 WSW-ENE. Evenly lit halo with a very small bright core.

400/500mm - 18" (11/22/03): moderately bright, moderately large, elongated 5:3 WSW-ENE, 1.5'x0.9'. Sharply concentrated with a bright 30" core which increases to the center. UGC 3127 lies 22' SW.

Notes by Steve Gottlieb