NGC/IC Project Restoration Effort

===== NGC 6766 = NGC 6884. Things were not looking good for this stellar planetary discovered by Pickering -- until Dave Riddle began digging around in the old literature. There he found a paper by the Reverend Thomas Espin (MNRAS 72, 150, 1911) in which Espin quotes Pickering as correcting the published position by one hour of time (20h instead of the original 19h copied into NGC). The corrected position is also the one which Pickering published in HA 60, where N6766 is tellingly out of numerical order, though without the additional NGC number (from Copeland whose position is good). Pickering's early method of finding the planetaries is interesting: he simply swept the sky looking through a low-dispersion spectroscope attached to his telescope. The stars' spectra would have appeared mostly continuous through his instrument, while the planetaries would still appear as stellar points because most of their visible light is concentrated in the emission lines of oxygen at 4958 and 5007 angstroms. Pickering later pioneered the use of objective prism photography, and several planetaries were found on Harvard plates as a result, primarily by Williamina Fleming.

===== NGC 6766 See observing notes for NGC 6884.