Sunday, November 22, 2015

Lyra - Abell 46 and the Abell Planetary Catalog

Abell 46
Image Steve Gottlieb
Abell 46 is a planetary nebula. The central star, V477 Lyrae, is an eclipsing post-common-envelope binary, consisting of a white dwarf primary and an oversized secondary component due to recent accretion. The nebula itself is of relatively low surface brightness compared to the central star, and is undersized for the primary's mass for reasons not yet fully understood. Wikipedia

The Abell Catalog of Planetary Nebulae was created in 1966 by UCLA astronomer George O. Abell (1927–1983) and was composed of 86 entries thought to be planetary nebulae that were collected from discoveries, about half by Albert George Wilson and the rest by Abell, Robert George Harrington, and Rudolph Minkowski.

"P48 1994 Jean Large" by Picture scanned from the original by Michael Vergara
Licensed under CC BY-SA 3.0 via Commons
The planetary nebulae were discovered before August 1955 as part of the National Geographic Society – Palomar Observatory Sky Survey on photographic plates created with the 48-inch (1.2 m) Samuel Oschin telescope at Mount Palomar.

Observing notes by Steve Gottlieb
Planetaries on the Abell list are best viewed with a large aperture telescope (e.g. 18-inch (0.46 m)) and an OIII filter.
Summer: 17.5: at 200x and 140x using an OIII filter appears faint, moderately large, ~50" diameter, round. Can hold continuously with averted vision and visible with direct vision. Did not look unfiltered for the mag 15 central star.

13: at 79x with OIII filter appears extremely faint, moderately large, 1.0' diameter, almost round, can barely hold steadily. Just visible using a UHC visible although appears near the visual threshold.
Steve Gottlieb

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