Aitken discovered one IC-object. Using Lick Observatory's 12" Clark-Refractor he discoverd the Planetary Nebula IC 3568 on August 31, 1900. While examinig Comet Borrelly-Brooks he found, that BD +83° 357 in Camelopardalis is surrounded by a small circular nebula. This was confirmed with the 36" Refractor the next night; see A New Planetary Nebula, PASP 12, 198 (1899) or AN 153, 367 (1900). IC 3568 was misclassified as a compact galaxy UGC 7731 in the Uppsala General Catalogue. The 12" was replaced in its dome by the 40" Nickel-Reflector in 1980.

Obituary: MNRAS 112, 271 (1952); PASP 64, 5 (1952)