John Herschel discovered NGC 1668 = h2663 on 1 Dec 1837 and logged "eF; R; attached to a star 14m". His position is 3' SE of ESO 251-030 = PGC 15957, and the description of the nearby star applies.

300/350mm - 14" (4/7/16 - Coonabarabran, 178x): faint to fairly faint, elongated 4:3 WNW-ESE, low surface brightness, weak concentration to the center, which contains a faint stellar ncleus. A mag 13.8 star lies 25" NNE of center and several mag 11-12 populate the field. NGC 1668 is the brightest member of Abell Galaxy Cluster S497.

Notes by Steve Gottlieb