Eyepiece Simulations
from "Eyepiece" by Steve Waldee


Copyright (c) 2007, Regina L. Roper & Stephen R. Waldee - All Rights Reserved



Planetary Nebula M-27 "Dumbbell" (NGC-6853)
in Vulpecula

INFORMATION ABOUT THIS OBJECT:

Sadly, the remarkable reds, yellows, blues, and greens that shine in observatory photos of M-27 are not detected by the eye in amateur-sized scopes. Some eagle-eyed observers may perceive a greenish cast, due to hydrogen radiation at 486.1 nm, to which the eye can be slightly sensitive at low levels; most viewers of the "Dumbbell" will notice only a variegated gray hourglass-structure, which closes to an irregular sphere in large scopes.

"Some of my readers may perhaps feel that I have allotted an undue proportion of space to minute and inconspicuous objects," wrote the Rev. T. E. Webb in Volume 2 of "Celestial Objects for Common Telescopes", originally published in 1859. "But... this list... will be closed with a nebula which I think will not be found disappointing."

Webb follows with an accounting of observations of M-27 by the major observers of the day: the Earl of Rosse (whose gigantic 72-inch speculum telescope was the most powerful astronomical instrument of the mid-19th century), Huggins, and other colleagues of Webb whose contributions are often forgotten in this CCD era. The reverend pastor concludes his book with a Latin panegyric by Kepler to the glories of the majestic firmament.

In the era before the final ascendence of Darwin's concept of the indeterminate universe, T. E. Webb, like most scientists of the day, voiced a romantic, poetic view of the inexpressible beauty of natural phenomena. How appropriate that he concluded with an account of nebula M-27: a gargantuan vista of exploding energy from glowing hydrogen, oxygen, and other white-hot elements, fluorescing from bursts of radiation from the dying star responsible for its glory, as it contracts into an unimaginably- dense white dwarf state!

One of Charles Messier's own discoveries, No. 27 seems much more than a comet-like smudge in today's amateur optics. Though rather difficult to locate in the rich star fields of Vulpecula, east of Cygnus and the summer Milky Way, the "Dumbbell" can be spotted in a lowly finderscope; in a 3" refractor it begins to resemble its appellation, while in a very large scope, the "Dumbbell" reveals a faint nebulosity completing the ellipse.

M27, under light pollution, with nebular filter, and in color photo

ABOUT THE IMAGES:

Jim Molinari of Cupertino, California, provided b&w images of M-27 for the eypiece-view simulations: with his Celestron C-8 telescope, a telecompressor providing a focal ratio of f/6.2, Konica 1600 film (sensitized with forming gas), he used an exposure time of 60 minutes.

PICTURE NO. 1 (middle): The "Dumbbell" as seen in an 8" or larger-aperture telescope, in moderately-dark skies, with about 75X magnification. The bi-nuclear shape is clearly detected, but the contrast is low.

PICTURE NO. 2 (right): A contrast-enhanced view under the same conditions above, with the addition of an oxygen-nebular-line filter, increasing the contrast of the doubly-ionized oxygen wavelengths by reducing skyglow and scattered light-pollution. The oxygen and hydrogen-line filters are effective in enhancing views of M-27, especially in suburban skies, when the correct eyepiece exit pupil range is utilized.

PICTURE NO. 3 (left): was processed from a color image taken by Ron Wood, at prime-focus of his 8" f/5.2 Newtonian, utilizing gas-hypered Kodak Ektapress 1600 film, and a 40-minute exposure.


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