Harold Corwin

IC 5163, IC 5164, and IC 5166 (with a faint companion star) are all single stars or, in the case of IC 5163, an asterism, near the nominal position for NGC 7210. Bigourdan actually found four objects here that he thought nebulous, but only three ended up in his list of "novae" and thus in the 2nd IC. The fourth (which he called "NGC 7210B" in his table) has only a single observation, while the others have two each.

However, IC 5163 is a curious case. Bigourdan's two observations of this object fall about 25 arcsec apart. He was not sure that they were the same object, speculated that they might be, but finally gave them separate numbers in his list of "novae". Dreyer combined them in the IC under the single number. I wonder if he asked Bigourdan about this.

It turns out that Bigourdan's observations refer to different parts of a line of three stars about an arcminute long. The first observation is closer to the northeastern of the stars, while the second is nearly on the middle star. This middle star has a companion much closer to the southwest than the northern, so is reasonably taken as a double star on the POSS/DSS.

― IC Notes by Harold Corwin

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