Harold Corwin

IC 400. Stone measured only the RA of this object, so the IC NPD is marked uncertain. In principle, the RA ought to be very good, as it was measured four times using a chronometer. Unfortunately, there is nothing at the derived RA anywhere near the nominal declination. Two seconds following, there is a faint late-type spindle, though it does not match the sparse description (m = 16.0, diameter = 0.1 arcmin) well. I also have my doubts whether the spindle could be seen visually, even with the 26-inch: its surface brightness is pretty low.

There is also a transcription error in the Leander McCormick list. The comparison star is called "CCO 228" at "04 55 03.54, -15 55 03.3" for 1890.0. Checking through the table, I noticed that CCO 228's declination is given differently in the observation for NGC 1730 (obs. no. 208): "-15 57 47.3". The declination of CCO 225 (in another observation of N1730, No. 203) is the same as that for the declination given for the comparison star of IC 400 (obs. no. 209), while the RA is different. So, which star did Stone use as a comparison for his new nebula?

Since he used CCO 225 (which is SAO 150054) only for the one observation of N1730 on a different night than he found IC 400, it is most likely that the correct star is CCO 228 (SAO 150066). This makes the RA of the spindle close to the measured RA -- but it is still far enough off to bother me. Is there significant proper motion for the star? Perhaps it has moved enough in the interval between early 1889 when Stone observed it, and 1950 -- the SAO epoch and equinox -- that it could account for the difference in RA.

The spindle has a faint companion about 20 arcsec southwest with a brighter star superposed. Is it possible that the combined image is actually Stone's object? It would be closer to his position than the spindle, but still a full second of time off.

Finally, Wolfgang chose a star for IC 400. I'm not convinced by this, either.

At the moment, I'm not willing to say which object -- if any -- is IC 400. There are just too many puzzles here.

― IC Notes by Harold Corwin

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

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