Harold Corwin

IC 3566 is probably a defect -- but just possibly may be a comet. Found by Frost on Harvard plate A6720 (10 May 1904), he described it as "Com., head R, tail 1.0' long at 110 deg." Adelaide Ames, in her 1930 catalogue of the Virgo Cluster, says simply "A comet" in her footnote to a list of NGC and IC objects which she could not find. She examined the same plate that Frost used.

Brian Skiff and Larry Wasserman at Lowell Observatory have run Frost's position (12 31.3 +11 43; 1900) through a comet identification program, and came up empty-handed. The nearest known comet was 10P/Tempel 2, but it was more than 15 deg away (at 13 36 11, +12 45.2) on 10 May.

On Brian Skiff's advice, I also asked Brian Marsden to run his software to check his comet catalogue. He wrote back, "I don't see any known comet that IC 3566 could have been."

So, it is almost certainly a defect on the old Harvard plate.

― IC Notes by Harold Corwin

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