Harold Corwin

NGC 16 = H IV 15 = h 4 = h 5. Here is a peculiar case where both WH and John Herschel have enough problems in their observations that Wolfgang Steinicke has suggested that John Herschel actually saw NGC 22 in one of his observations rather than the much brighter galaxy that his father found. Courtney Seligman brought this to my attention in April 2015; see his web page on the object for his take on the problems.

WH first saw this on 8 September 1784 and put it 2 minutes 6 seconds east of, and 1 degree 21 arcminutes south of alpha Andromedae. There is nothing there. But about 1 minute and 24 seconds west is found a galaxy more or less matching his description in CH's fair copy: "Stellar, or rather like a faint star with a small chevelure and two burs [sic]. F, S." There are a couple of additional things to note. First, there is another star in the sweep, 85 Pegasi that gives a different RA zero point. Using that, the position for WH's object becomes just 1 minute 6 seconds west of the galaxy. This is strongly suggestive of a simple digit error in WH's observation.

The next observation was by John Herschel on 5 September 1828. This pinned down the galaxy very well, but John Herschel added a note in parentheses to his observation, "(?[query] if not IV 15)", well aware that his position was well off his father's.

John Herschel went over the field again on 16 September of the same year, but recorded only an approximate position for the object, calling it "A star 15m with a burr AR [sic] from Cat." So, he accepted that he had seen the same object in this sweep that his father had, even to the extent of adopting the RA from his father's list. There is, of course, nothing in this position.

And this is where the trouble really sets in. John Herschel enters the two observations in his own 1833 list as two separate objects, and copies both into the GC. d'A comments that he cannot find GC 12 = h 5 on three of the five nights that he observed an object which he called H IV 15 = h 4, not following John Herschel's own list where he (John Herschel) put IV 15 = h 5. John Herschel has a rather peeved note in GC about this: "D'Arrest says, 'h. II. positio cert erronea,' but gives no indication of the correction required in R.A. or P.D."

Dreyer finally sorts it all out for the NGC by making IV 15 = h 4 = h 5, adopting something of a mean of John Herschel's and d'A's positions, and adding a note, "h 5 was not seen by d'A [3 nights] and St[ephan] (XIII) [2 nights]; it is = h 4 as they were observed in different sweeps." In his 1912 edition of WH's complete scientific papers, he adds "IV 15 is = h 4, 1m 20s p[receding] H's place. Some error in recording the transit, probably of 1m; reductions correct."

So there matters stood until Wolfgang went over the field during his re-evaluation of WH's observations and decided that IV 15 = NGC 22. He also, in his re-evaluation of John Herschel's observations, has h 5 identical to a star at 00 10 28.0, +27 42 00 (there are neither stars nor galaxies there). I have not yet had any correspondence with him about this; but given that WH's declination is off NGC 22 by 7 arcmin, and that a simple 1 minute of time RA error will explain the difference in position with NGC 16 -- well, I find myself agreeing with Dreyer on this one.

― NGC Notes by Harold Corwin

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