Harold Corwin

IC 759 has to be marked "not found." This is another of only seven of Bigourdan's new objects for which he provides no details in his big tables of differential positions (see IC 532 for a general note on these objects). The only information we have comes from his Appendix VII in his Introductory volume, his second list of new nebulae published in "Comptes rendus", and the first IC, which Dreyer, of course, took from the "Comptes rendus" list.

The NGC description reads "pB, pL, Epf." In Appendix VII, we also find that the magnitude is 12.7, and a remark, "Fausse image?" Added to this is the information that Bigourdan apparently found this while observing NGC 4086 -- but he provides no differential positions for that object, either. So, the possibilities come down to these: 1) Was this perhaps a false image caused by a reflection from SAO 082124 (at about the same declination)? 2) is the object actually NGC 4086? or 3) is it the faint galaxy at 12 02 41.9, +20 35 21 (B1950.0). None of these seem particularly likely.

Finally, to finish with a curious "coincidence," Bigourdan dates this discovery to 23 March 1887, the same evening on which he found IC 532 and IC 543 (which see). Bad seeing, maybe? Lost observing book? There are any number of possibilities.

In August 2016, I finally found Bigourdan's original observation in his Appendix VIII, the "Complementary Measures". He has the object -4.69 seconds and -2' 11.8" from HD 104958 = SAO 082124. There is nothing in this position. He has this to say about the object: "Pretty extended nebula, irregular, elongated at 99 degrees, and with [diameters] 1.5 [arcmin] x 40 [arcsec]; it is diffuse, slightly brighter towards the center, without a nucleus. It is not amenable to precise measurement."

He also observed NGC 4090 on the same night, using the same comparison star. His position for that galaxy, from two measurements, is within 2 arcseconds of the modern position. I suppose he could have confused his stars, but this seems very unlikely.

His final assessment "Fausse image?" is certainly correct, but tells us nothing about what he actually saw. See my previous speculation just above. In any event, IC 759 does not exist.

― IC Notes by Harold Corwin

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