George Johnstone Stoney or his brother Bindon Stoney discovered NGC 5542, along with NGC 5538, on 6 Mar 1851. While observing the field of NGC 5546 he noted "another 5' preceding NGC 5546]." There were no later observations to determine a more precise position. Heinrich d'Arrest measured an accurate position (3 observations in 1865) and noted it preceded NGC 5546 by 16-17 sec of RA.

400/500mm - 17.5" (7/17/01): fairly faint, small, slightly elongated, 0.7'x0.5', small bright core. In a trio with NGC 5546 4.0' E and NGC 5543 6.4' NE. Accidentally ran across the trio while looking for NGC 5528.

17.5" (5/10/91): very faint, very small, round, weak concentration. In a trio with NGC 5546 4' E and NGC 5538 6' SW.

Notes by Steve Gottlieb