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Pickering discovered 15 NGC and 2 IC-objects. All NGCs (exept one) are Planetary Nebulae, found by visual spectroscopy at the 15" refractor of Harvard College Observatory. NGC 6879 was also detected with this method by Copeland on Sep. 17, 1884. The 2 ICs were discovered on a plate made at Arequipa of the Eta Carinae region.
Tab. Pickering's discoveries (No. refers to the numbers given in Ref. 5, HN = "Harvard nebula" is from Ref, 10)
| Object | No. | HN | Con |
Date | Type | Ref |
| NGC 6439 | 8 | 48 | SGR |
Aug. 18, 1882 | planetary nebula | 3, 5, 10 |
| NGC 6537 | 5 | 45 | SGR |
Jul. 15, 1882 | planetary nebula | 2, 5, 10 |
| NGC 6565 | 2 | 42 | SGR |
Jul. 14, 1880 | planetary nebula | 1, 5, 10 |
| NGC 6567 | 9 | 49 | SGR |
Aug. 18, 1882 | planetary nebula | 3, 5, 10 |
| NGC 6578 | 7 | 47 | SGR |
Aug. 18, 1882 | planetary nebula | 3, 5, 10 |
| NGC 6620 | 3 | 43 | SGR |
Sep. 3, 1880 | planetary nebula | 5, 10 |
| NGC 6644 | 1 | SGR |
Jul. 13, 1880 | planetary nebula | 1, 5, 10 | |
| NGC 6741 | 10 | 50 | AQL |
Aug. 19, 1882 | planetary nebula | 3, 5, 10 |
| NGC 6766 | 53 | LYR |
May 8, 1883 | not found | 7, 10 | |
| NGC 6790 | 6 | 46 | AQL |
Jul. 16, 1882 | planetary nebula | 2, 5, 10 |
| NGC 6803 | 12 | 52 | AQL |
Sep. 17, 1882 | planetary nebula | 6, 10 |
| NGC 6807 | 11 | 51 | AQL |
Sep. 4, 1882 | planetary nebula | 5, 10 |
| NGC 6833 | 54 | CYG |
May 8, 1883 | planetary nebula | 7, 10 | |
| NGC 6879 | 55 | SGE |
May 8, 1883 | planetary nebula | 8, 10 | |
| NGC 6881 | 4 | 44 | CYG |
Nov. 25, 1881 | planetary nebula | 4, 5, 10 |
| IC 2581 | CAR |
May 10, 1893 | open cluster | 9 | ||
| IC 2599 | CAR |
May 10, 1893 | emission nebula | 9 |
References: [1] New Planetary Nebulae, Obs. 4, 81-83 (1881); [2] New Planetary Nebulae, AN [2454] 103, 95 (1882); [3] New Planetary Nebulae, AN [2459] 103, 165 (1882); [4] New Planetary Nebula, Obs. 5, 26-27 (1882); [5] Small Planetary Nebulae discovered at the Harvard College Observatory, Obs. 5, 294-295 (1882); [6] Small Planetary Nebula, Obs. 5, 342-343 (1882); [7] New Planetary Nebulae, AN [2517] 105, 335 (1883); [8] Mem. Roy. Astr. Soc. 49, 8- (1888); [9] Progress during the years 1891 to 1894, Ann. Harv. Obs. 26, 197-212 (1891); [10] Nebulae discovered at the Harvard College Observatory, Ann. Harv. Obs. 60, 147-194 (1908)
Dreyer credits Pickering for 15 other IC objects: IC 418 in Lepus, IC 420, 421, 423, 424, 426, 427, 428, 430, 431, 432, 434, 435 in Orion, IC 1266 in Ara, and IC 1297 in Crater. All were found by Williamina Fleming, with one exception (IC 434), which was detected much earlier by William Herschel.
Obituary: PASP 31, 73 (1919); MNRAS 80, 360 (1920); ApJ 50, 233 (1919); AN 298, 131 (1919)
