The first IC adds "In Swift's list IX the declination for 1890 is given as 63 32.6. It was 62 in the MS. communication sent me in 1887" (which of the two values might be correct not being indicated in the addition). The second IC lists a corrected position (per Bigourdan) of RA 16 13 47, NPD 26 55.

At less than 6000 light years distance, M4 is the closest globular cluster to the Sun. One result of this is that white dwarfs, which are among the faintest stars actually visible in any given region of space, can be imaged in the cluster. By studying the properties of M4's white dwarfs, the age of the cluster can be determined (the oldest white dwarfs presumably being about the same age as the cluster). This yields an age of 12 to 13 billion years, which is almost as old as the Universe, and taking into account the time it would take clusters to form, implies that the stars in M4 are among the oldest known to exist.

Below, part of the NOAO image of M4 is shown, with a box indicating the location of the HST image of the cluster at lower left. The box in that image indicates the region shown in even greater detail at lower right, in which the white dwarfs used to determine the age of the cluster are circled. The extreme faintness of the white dwarfs makes most of them hard to see even in the lower right image; and none are visible at all in the other, more normally exposed images. (Image Credits: NOAO image, NOAO/AURA/NSF (as in the image at top); HST image, H. Richer (U. of British Columbia, NASA)

The second IC lists a corrected NPD (per Bigourdan) of 51 52.

Per Dreyer, NGC 6124 is a "cluster, bright, large, pretty rich, a little compressed middle, stars from 9th to 11th magnitude". The central concentration covers less than half a degree, but the overall extent of the cluster is about 40 arcmin.

Stephan made a huge error (a whole hour of right ascension) in converting the telescopic observation of his "2-2" to a fixed place in the sky, presumably (per Corwin) due to a misidentification of the comparison star used to establish the position of the nebula. As noted in the discussion of NGC 218, sometime before 1914 a student assistant at the Marseille Observatory, Emmanuel Esmiol, was given the task of collecting all of Stephan's observations and converting them to the 1900 Equinox. In doing so, Esmiol discovered and corrected a number of errors in Stephan's reductions (that is, the conversion of his raw observations to accurately calculated positions). In the present case, Esmiol noted that NGC 6138 was the same object as NGC 6263. Unfortunately, that statement was also incorrect, presumably due to a printing error; for as related by Corwin, a recent investigation by Gottlieb and Highe shows that the field around NGC 6263 does not resemble Stephan's description of the region around NGC 6138, but instead matches that around NGC 6363. Needless to say, a decade before Esmiol published his results and a century before the truth of the matter was discovered, neither Stephan nor Dreyer had any way of realizing that NGC 6138 and 6363 were the same; so the double listing was an inevitable result. (Note: The fact that the true identity of NGC 6138 was unknown for so long means that the label has been incorrectly applied to a completely different galaxy (PGC 58070) for quite some time; and as a result, almost any search for NGC 6138 will refer to that galaxy, instead of the correct one. For that reason, any future reference to NGC 6138 should be to NGC 6363, instead.)

Based on a recessional velocity of 9955 km/sec, PGC 58070 (incorrectly listed as NGC 6138 in almost every current reference) is about 460 million light years away, in good agreement with a redshift-independent distance estimate of 445 million light years. Given that and its apparent size of 1.2 by 0.25 arcmin, it is about 160 thousand light years across.

Based on a recessional velocity of 15375 km/sec, a straightforward calculation indicates that NGC 6148 is about 715 million light years away. However, for objects at this distance we must take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 685 million light years away at the time that the light by which we see it was emitted, about 705 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of 0.45 by 0.25 arcmin, NGC 6148 is about 90 thousand light years across.