IC 4471

History and Accurate Positions for the NGC/IC Objects (Corwin 2004)

IC 4471 = NGC 5697. Bigourdan went over this area on two nights. On the first, 6 June 1894, he found a faint nebula that he could not measure because of a poor sky. He estimated its position as 30 seconds of time following and 36 arcsec south of BD +42 2516. This is close to a double star about 0.8 arcmin southwest of NGC 5697. However, that estimated position has relatively large errors, and Bigourdan did not mention NGC 5697 itself in his descriptive note. He does, however, say, "[The nebula] is preceded by a star 11.5 situated in the middle of the distance between BD +42 2516 and this nebula."

That star is his comparison star for his measurements of NGC 5697 on the second night, 4 May 1899. His reduced observation places the galaxy within a few arcsec of the modern position (surprisingly, the galaxy is in the Tycho-2 star catalogue; is there a star superposed, or does it have a stellar nucleus?). However, on this night, Bigourdan claims that he did not see the faint nebula that he found five years earlier. Nor does he mention the new nebula in his note for NGC 5697.

His note on the second night for IC 4471, his "nova," reads in full: "Not seen; [then, in italics] I looked for it preceding the star BD +42 2516." I think that during preparing his observations for publication, he realized his mistake and inserted the italicized part of the note.

In any event, he never observed more than one nebula at a time in this field. Also, the combined magnitude for the double star (15.6) is about a magnitude fainter than the magnitude for NGC 5697 (14.7). So, I think that his observations for his "nova" and for NGC 5697 actually refer to the same object.