Harold Corwin

Corwin: IC 2603 does not exist. Though Bigourdan has two micrometric measures of it on the night of 27 March 1887, as well as a plausible description, he failed to find it again on nights in 1899 and 1907. His note reads (translated by me from the original French),

Diffuse nebulosity, elongated at 98.9 deg (measured PA = 97.42 deg, 1 pointing), about 1.4 arcmin long by 40 arcsec wide. It could be formed by 2 nebulae nearly in contact; the following one is a little brighter and more extended. Could be a false image.

His final sentence, with his own italics added for emphasis, says it all.

My suggestion that this could be a star 47 arcsec from the IC position (from many years ago when I was young and naive) is wrong. Since that more innocent age, I've discovered Bigourdan's massive set of observations, and have learned how to use them. It's clear that IC 2603 really is non-existent. It's still not clear, however, just what these "fausses images" of Bigourdan's actually were. I suspect some sort of internal reflection in his telescope -- the 30-cm refractor at Observatoire de Paris -- but that is just a guess. IC 2610 is another such object; see that for similar speculation.

― IC Notes by Harold Corwin

Harold Corwin

IC 2605 is probably the southwestern arm of NGC 3395. Bigourdan saw it only once on 11 April 1899, commenting, "Nebulous rounded object, about 20 arcsec across, it would be nearly impossible to make measurements." Indeed he did not, leaving us an estimated offset -- 0.5 seconds of time west, and 17 arcseconds south -- from the nucleus of NGC 3395 itself. In March of 1907, he could not find it again, simply saying, "Not seen."

The line of three knots in the southwestern arm that I had identified earlier as IC 2605 is NOT the "object" that Bigourdan saw. His is the brighter arm closer in to the center of the galaxy, and that is the one that I've finally given a position for in the table.

― IC Notes by Harold Corwin

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