NGC/IC Project Restoration Effort

===== NGC 6139 is a bright, small, compact globular cluster discovered by James Dunlop in the 1820s. JH recovered it June of 1834 with observations in three successive sweeps over four days. His mean position is just 0.6 arcminutes north of the center of the cluster, so there is no problem with the identification. However, the positions from the 2MASS lists and UCAC fall 0.3 seconds of time west of that given by GSC-A and by examination of the DSS images. SIMBAD adopts the 2MASS XSC position, but that is clearly off the middle of the image they display, whether from DSS or 2MASS. The mean difference for several nearby stars for sources HCsv, GSCA, and GSC3; compared with 2MSP, UCAC, and UB10 is 0.00 seconds in RA and 0.0 arcseconds in Dec -- in other words, the problem occurs only for the globular cluster. There is no apparent clump of stars to the west that might cause the problem, so the difference remains a mystery. Until it is solved, I'm going to trust my eyes, and adopt the GSC-A position. Hopefully, some of the dynamicists will get around to this cluster soon to use a more rigorous algorithm to find the cluster's central position.

===== NGC 6139 18" (7/10/02 - Magellan Observatory, Australia): this is a moderately bright globular which is well concentrated to a bright 1' core. The halo spans ~3.5' and the overall structure is symmetric. A number of very faint stars blink in and out of view with the seeing and it appears on the verge of extensive resolution at 171x. Did not view with higher power. 8" (6/27/81): faint, small, even concentration to core, easily visible but no resolution.