Harold Corwin

IC 3999 is probably identical to NGC 4862 (which has its own story). Bigourdan has only a note on the object in his big table, claiming the object to be +30 seconds and +3.7 arcmin from BD -13d 3633. This observation is dated 16 April 1895. However, referring to his table of novae, Bigourdan makes the date 12 May 1885. There is no trace of this other observation in his published tables, including his list of supplementary observations in Appendix 8 of his introduction. So, the 1895 observation is all that we have to go on for details.

At Helwan and Mt. Wilson, observers chose the star close to the nominal position as the object. Wolfgang Steinicke and I made a different choice, the faint galaxy 7 seconds east and 4 arcmin south of the nominal position. Finally, Malcolm Thomson noticed that if the sign of Bigourdan's estimated RA offset is changed to a minus sign, the position is close to NGC 4862, a faint spiral found by Frank Leavenworth at Leander McCormick (the galaxy is positively identified by Leavenworth's sketch; as usual, the nominal position is off in RA).

Malcolm's idea is given added support when we look at Bigourdan's attempts to locate NGC 4862 -- he did not find the galaxy on two nights. On the first night, however, he searched at the offset of +10 seconds and +4 arcmin from the same BD star, and made a specific note that he did so. This is the wrong direction, however, so on the second night, he searched at -10 seconds and +4 arcmin. It was on this second night that he "... suspected a trace of nebulosity in the neighborhood of a star, magnitude 13.4, located at ..." the offsets noted above. Since he had his offsets confused for one night, it seems reasonable that he might have done the same the second.

In any event, reversing the sign of his estimated RA offset puts his suspected object within an arcminute of NGC 4862. Thus, the identity is reasonable, so I've adopted it, though with a colon flagging the remaining uncertainty.

― IC Notes by Harold Corwin

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