Harold Corwin

IC 4591, IC 4592, IC 4601, IC 4603, IC 4604, and IC 4605 are all part of the great complex of nebulae around rho Ophiuchi in the general area of Antares. Though discovered visually by Barnard while he was sweeping for comets, the nebulae are too faint to be clearly seen by eye. So, Barnard's descriptions, published first in AN 3001 and a few months later -- with photographs -- in MN, come from his early Lick plates of the area. Interestingly, Stewart also examined a plate of the area, his taken from Harvard's Arequipa Station in Peru, but found only IC 4601 on it. His plate was a one-hour exposure, while Barnard was able to expose for two-plus hours with a faster camera for his discovery plates. Barnard's 6-inch Willard portrait lens also gave a considerably larger field of view, roughly 12 deg by 10 deg (at least as reproduced in Vol. 11 of the Lick Publications). Stewart worked with a field of 6.4 x 6.4 degrees, coincidentally very close to that of the Palomar and Southern (Siding Spring) Sky Surveys.

Barnard's descriptions, while very sketchy and qualitative, are adequate to identify the nebulae, and his positions refer to the stars involved in the brighter parts of the nebulosity. Dreyer generally adopted positions for the stars as given in Barnard's papers, so I've followed along using positions from Tycho-2 for the same stars. I've taken mean values when necessary.

― IC Notes by Harold Corwin

Drawings, descriptions, and CCD photos are copyright Andrew Cooper unless otherwise noted, no usage without permission.

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