NGC 6543, mag. +8.2, also known as the Cat's Eye Nebula is a planetary nebula located in the northern constellation of Draco. It was discovered by William Herschel on February 15, 1786 and is one of the brightest and finest examples of its type. Some of the most spectacularly images ever taken by the Hubble Space Telescope have been of NGC 6543, which display a wealth of exquisite details across a large complex eye-like structure.
In total, the extended halo of the nebula spans some 6.5 arc minutes of apparent sky. However, through amateur scopes only the small inner section is visible (approx. 20 arc seconds) and therefore it appears tiny and considerably smaller in apparent size than for example, Jupiter. However, the advantage of a compact centre is high surface brightness, and therefore NGC 6543 can be spotted with binoculars and is easily visible through small scopes.
The Cat's Eye is located in a barren region of sky near the centre of sprawling Draco. It's positioned 13 degrees north of Eltanin (γ Dra), which at mag. +2.2 is the brightest star in the constellation. The nebula lies between delta (δ - mag. +3.1) and zeta Dra (ζ - mag. +3.2) and at about the centre point of an imaginary line connecting 5th magnitude stars, 27 Dra and 42 Dra. Interestingly, NGC 6543 sits nearly exactly on top of the ecliptic north pole. It's best seen from the Northern Hemisphere during the months of June, July and August and is circumpolar from latitudes above 24N.
In most scopes, NGC 6543 appears as a tiny, bluish green spot of bright nebulosity. An 80mm (3.1-inch) refractor reveals an evenly lit slightly small oval disk that responds well to high power. On initial inspection it may appear stellar, but higher magnifications easily reveal its true nature. A 200mm (8-inch) scope hints at some colour but generally larger instruments of at least 300mm (12-inch) are needed to tease out the finer details. Although the central star shines at mag. +11.4, it takes a large instrument at high powers to spot it due to the overwhelming brightness of the surrounding nebula. Of course, even on the best nights, NGC 6543 won't look anywhere near as spectacular as seen in Hubble images.
NGC 6543 is 3,300 light-years distant and is estimated to be about 1,000 years old. It has a temperature between 7000 and 9000 K, which is hotter than the surface of the Sun. In the Caldwell catalogue the object is listed as number 6.
NGC 6543 Data Table
|Name||Cat's Eye Nebula|
|Object Type||Planetary Nebula|
|RA (J2000)||17h 58m 33s|
|DEC (J2000)||66d 38m 00s|
|Apparent Size (arcsecs)||20 x 16 (centre)|
|Radius (light-years)||0.15 (centre)|
|Other Names||Snail Nebula, Sunflower Nebula|
|Features||Central star mag. +11.4, positioned close to Ecliptic North Pole|