6 Attachment(s)
Object of the Week, September 28, 2014 - NGC 6543
NGC 6543
Planetary nebula
Draco
RA 17h 58m 33s
DEC +66° 37′ 59.5”
Magnitude: 8.1
Size: 20”
Attachment 1381
"On the evening of August 29, 1864, I directed the telescope...to a planetary nebula in Draco [NGC 6543]. The reader may be able to picture to himself...the feeling of excited suspense, mingled with a degree of awe, with which, after a few moments of hesitation, I put my eye to the spectroscope. Was I not about to look into a secret place of creation?
"I looked into the spectroscope. No such spectrum as I expected! A single bright line only! ... The light of the nebula was monochromatic, and so, unlike any other light I had yet subjected to prismatic examination, could not be extended out to form a complete spectrum...A little closer looking showed two other bright lines on the side towards the blue. The riddle of the nebulae was solved. The answer, which had come to us in the light itself, read: Not an aggregation of stars, but a luminous gas."
So wrote William Huggins in his 1897 memoir after being the first person to show that not all nebulous objects were clusters of faint stars that merely needed a larger telescope for resolution, a view held by many astronomers until this singular observation. In 1863, he and his collaborator W.A. Miller had been the first to spectrographically show that stars were made of the same basic stuff as the Sun, so this discovery cemented Huggins, and NGC 6543, in astronomical history.
Even without knowing the role 6543 played in getting modern astrophysics started, it’s a visual treat through just about any size scope. This past August I made this sketch at the Oregon Star Party that hints at the overall detail that’s available in 6543. I used magnifications up to 1210x because the image scale made it easier to see the overall structure. Unfortunately, the seeing wasn’t steady enough to reveal the helical loops seen by Uwe in his sketch with his 27 inch as seen at:
http://www.deepsky-visuell.de/Zeichn...NGC6543_27.htm
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I did glimpse this intricate internal detail briefly on a nearly perfect night at Steens Mountain with my old 20 inch years ago, and I’ve observed 6543 on many occasions since then hoping to recapture that view. So far no luck, darn it!
I’ve also included this sketch made by H.D. Curtis at Lick Observatory that was made from a series of small photographs of different exposures using the Crossley 36 inch reflector in 1918. Although Curtis’ drawing has more of a corkscrew shape than my sketch, it’s more similar to my sketch than to the iconic HST photo at the beginning of this post.
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On the other hand is the faint, circular halo that surrounds the brighter part of the planetary in my sketch that’s also shown so prominently in the HST image as a series of concentric halos sliced by innumerable straight rays converging on the bright central star. Has anyone observed any of this beautiful detail?
Further out is the extended halo of 6543, which stands out impressively in a sufficiently large scope (i.e. the 90 inch Bok). The Bok clearly showed IC 4677 is merely the brightest part of this large, scalloped ring, which I’ve only been able to see half of in my 28 inch. IC 4677 is in the upper right part of the extended halo in this sketch of my view through the 90 inch.
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Over the years I’ve consistently described the overall color of 6543 as a bright blue-green, especially at lower powers, but on several occasions it’s retained its color at higher power as well. My hunch is that this depends a great deal on the transparency of the sky.
My best views of NGC 6543 have always been without a filter, mostly to preserve the color but also to see the most detail. What's been your experience?
"GIVE IT A GO AND LET US KNOW"
