In general, wide-field images are centered on or close to the "Near J2000 RA xx xx xx, Dec xx xx xx" position. When the positions listed in Hickson's original paper are reasonably close to the Hickson Compact Group in question, the "Near" position is merely a conversion from 1950 to 2000 coordinates. Where such a conversion results in a position well off the mark, a brief note discusses the problem (e.g., an inadvertent repeat of the RA for HCG 2 replaced the RA for HCG 3, and the RA for HCG 3 ended up replacing the RA for HCG 4).
 "Empty" data tables have four "entries" because Hickson Compact Groups always contain at least four galaxies.

HCG 2d is a much more distant background galaxy, and not actually associated with the other galaxies.

HCG 3c must be a considerably more distant background galaxy.

HCG 4a and 4d appear to be a moderately distant pair, HCG 4c and 4e a very distant pair, and HCG 4b is probably a foreground galaxy.

HCG 5d is a foreground galaxy.

HCG 9b and 9c may be a pair, but HCG 9a and 9d are probably isolated galaxies.

HCG 11a is a foreground galaxy, 11b and 11c are a distant pair, and 11d is about halfway between the nearer and further galaxies.

HCG 14d is a background galaxy. Note: LEDA incorrectly reverses designations for HCG 14a and 14b.

HCG 15c is a background galaxy.

 The southwestern and southeastern members of the group (PGC 34882 and NGC 3653) appear to be background galaxies, but the other members of HCG 51 are a physical group and clearly interacting, as the region between NGC 3651 on the east and IC 2759 on the west shows considerable extensions of stellar material torn from the galaxies by their interaction.

"70g" is in quotes because it is not shown in Hickson's paper; but some HCG catalogs include it with the group despite that. Per Corwin, the three IC identifications have been badly mangled in numerous references (e.g., LEDA has the correct PGC IDs, but incorrect IC IDs), and other references also mislabel the various HCG components in one way or another. As it happens, HCG 70 is actually two sets of galaxies, a trio consisting of HCG 70a, b and c (the larger galaxies at center and left of center), and a more than twice as distant quartet consisting of the other "members" of the Group (the four "smaller" galaxies, not really smaller but simply further away).

HCG 73a is much closer than HCG 73b, c and d, and HCG 73e is much further away, so the "group" is actually 3 galaxies at similar distances (73b, c and d), a much closer object (73a) and a much more distant object (73e), and not a quintet.