Harold Corwin

IC 2216 is a double star. Curiously, Bigourdan's reduced position fell nearly 2 seconds of time east of the star. I finally noticed, though, that his column headed "Delta RA/sec Dec" was, for this object, considerably different from his "Delta RA" column on the following page. Instead of dividing by the secant of I2116's declination, he seems to have divided by the secant of the declination of the next object in the list, NGC 2505 at +53 degrees. Thus, instead of the correct Delta RA of +3.84 seconds (a mean of four micrometer readings), he has +6.51 seconds in his table.

Once this change is made, his RA ends up exactly on the double star, and all doubt as to the identity of I2216 vanishes. It was pretty clear in any case, as Bigourdan notes a triangle of stars 1.3 arcmin in PA = 40 degrees from his "nova" -- that triangle is just where he put it.

― IC Notes by Harold Corwin

Harold Corwin

IC 2216 is a double star. Curiously, Bigourdan's reduced position fell nearly 2 seconds of time east of the star. I finally noticed, though, that his column headed "Delta RA/sec Dec" was, for this object, considerably different from his "Delta RA" column on the following page. Instead of dividing by the secant of IC 2116's declination, he seems to have divided by the secant of the declination of the next object in the list, NGC 2505 at +53 degrees. Thus, instead of the correct Delta RA of +3.84 seconds (a mean of four micrometer readings), he has +6.51 seconds in his table.

Once this change is made, his RA ends up exactly on the double star, and all doubt as to the identity of IC 2216 vanishes. It was pretty clear in any case, as Bigourdan notes a triangle of stars 1.3 arcmin in PA = 40 degrees from his "nova" -- that triangle is just where he put it.

― IC Notes by Harold Corwin

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