Harold Corwin

I had suggested that this may also be NGC 1909, but consulting the Herschel Archive has disabused me of THAT idea. See the note for NGC 1909 for the story.

About IC 2118 itself, Max Wolf notes in his MNRAS discovery paper that NGC 1779, NGC 1797, and NGC 1799; as well as IC 398 and IC 402 are involved with this large nebula. All of these, of course, are galaxies which we see through the Galactic diffuse nebulae spread over the area.

The nebulosity is BIG, approximately 3 degrees long, stretching primarily northeast to southwest. The brightest portion is more or less straight east of psi (65) Eridanus, and it is to this area that I've assigned the position. The IC position, apparently estimated by Dreyer from Wolf's sketch, is a bit too far east -- it precesses to 05 06.7, -07 14 for J2000. I would put it closer to 05 05.2, -07 00 based on the sketch.

― IC Notes by Harold Corwin

Harold Corwin

William Herschel has one observation of this "Strongly suspected nebulosity of very great extent." He makes its size "Not less than 2 deg 11 arcmin of PD and 26 sec of RA in time." These numbers come from his offsets from Rigel: 11m 09s east to 11m 35s east, and 1 deg 19 arcmin north to 52 arcmin south.

While this whole area is covered with a very diffused, very low surface brightness nebulosity, I do not see anything that William Herschel could have seen easily. In particular, there is no nebula stretched out north to south as William Herschel describes.

However, at about the right distance WEST of Rigel, there is such a nebula, IC 2118. It is bright enough that William Herschel might have seen it during his sweeps, and it more or less matches his description. So, I am going to suggest, pending visual confirmation, that IC 2118 is the object William Herschel found, and that he somehow confused "east" and "west" in his log book.

That is what I wrote in the 1990s when I went over the field on the first Palomar Sky Survey prints. However, I now have Caroline Herschel's fair copies of the sweeps available and find that my idea of the nebulosity west of Rigel being William Herschel's object is impossible. William Herschel observed the nebulosity at least 11 minutes AFTER Rigel had left the field, so NGC 1909 cannot be west of the star. So, there is no possibility that William Herschel's object is IC 2118.

So what DID William Herschel see? Probably nothing beyond optical (reflections of bright stars, fogging of his eyepiece or mirror, faint clouds or sky glow) or physiological/psychological (aberrations within his eye, fatigue, hunger, etc) effects.

― NGC Notes by Harold Corwin

Drawings, descriptions, and CCD photos are copyright Andrew Cooper unless otherwise noted, no usage without permission.

A complete list of credits and sources can be found on the about page