Harold Corwin

NGC 3643, NGC 3644 = IC 684, and NGC 3647. Even though Marth's positions for NGC 3643, NGC 3644, and NGC 3647 are pretty good, this has not prevented later observers from misidentifying these at one time or another. In particular, Bigourdan's "NGC 3647" is a star, and he labeled NGC 3644 as "new" (his positions for both are accurate). Thus, this latter galaxy received an IC number (684) as well as its NGC number. Kobold got the right galaxies for N3643 and NGC 3644, but both he and Wirtz list NGC 3644 as "NGC 3645(?)" (though Kobold does have an erratum saying that though the identity is uncertain it is probably NGC 3644). RNGC has misidentified NGC 3643 and NGC 3645 (which see), and CGCG makes yet another object in the group NGC 3645.

Finally, just about everyone, including me, has misidentified NGC 3647. There are four CGCG galaxies here. Most of us have chosen CGCG 039-141 -- the easternmost -- but the brightest (by half a magnitude) of the three is CGCG 039-135, the westernmost. Steve Gottlieb has gently reminded us that brighter objects are usually easier to see than fainter ones. Even with a 48-inch reflector, Marth called this one an "eF neb *." And he saw only one object here, not four, so the obvious choice is the brightest.

― NGC Notes by Harold Corwin

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