|M57 "Ring Nebula": Planetary Nebula (Lyra) RA: 18h 53.6m / DEC: +33° 01'.8|
Instrument: 10-inch Starfinder
M57 is the most observed planetary nebula in the night sky. One reason is that it is very easy to find. The nebula sits between two bright stars in Lyra, 3.5 magnitude Sheliak and 3.3 magnitude Sulafat. The drawing at left is based on a 388X view (8.8 mm UWA with a TeleVue 3X Barlow) in my 10-inch, f/4.5 Meade Starfinder equatorial Newtonian. The drawing covers a 13' diameter area and is oriented with north up and east to the left. This magnitude 8.8 planetary nebula displays an oval shape elongated across an 130"x90" area. A 40" diameter inner region is surrounded by annular nebulosity. Subtle, faint lobes at the east and west limit of the annulus give the nebula an elongated appearance.
The 15.2 magnitude central star of the Ring Nebula is a difficult detection unless conditions feature both good transparency and steady seeing. I was able to detect the central star on this night and suspect an 8-inch aperture could do the trick.
I used several faint field stars of known magnitude to confirm my sighting of the central star. All can be found in a photograph on page 102 of the September 2001 issue of Sky & Telescope magazine. Magnitude 13.0 GSC 2642-0433, is visible near the eastern edge of the nebula. A magnitude 14.1 star is seen 100" south of GSC 2642-0433. A 13.4 magnitude star is visible 150" further along the same line. A trio of faint stars forms a right triangle that points toward the western edge of the nebula. Of these, the two closest to each other at the north end of the asterism have visual magnitudes of 14.7 and 15.3, respectively. The third star in this trio shines at magnitude 15.7. It is also fairly close to M57, residing just 15" to the northwest. A much brighter star is seen embedded within the southwest lobe of the Ring nebula. Visible 40" south of this star, is a magnitude 15.6 star.
Among the comparatively bright stars rendered in the drawing is a pair just inside the western field boundary. They are separated by 2'.2 and shine at magnitudes 12.3 and 11.6, respectively. The southern star is brighter. A mid-13th magnitude star is visible 2' east of the 11.6 magnitude star. Field stars with known visual magnitudes can be a big help in determining if that faint target was actually observed. In this case, my drawing includes three stars fainter than the central star in the Ring nebula. Two are at least half a magnitude fainter. This gives me confidence that my detection of the central star in M57 was genuine and not a case of averted imagination.
|Instrument: 18-inch Obsession|
Here's an observation with the 18-inch Obsession at 399X (18-mm SWA w/ 3X Barlow and Paracorr). The trio of 14.7, 15.3 and 15.7 magnitude stars is obvious in this aperture at high magnification. The double star positioned 1' north of the Ring is also seen. Of greatest interest, the central star is held consistently with averted vision during extended periods of improved seeing. Several observers confirmed this detection of the central star, which was made at the 2005 Lowell Star Party. The Ring nebula also shows some interesting detail. The northern and southern arcs appear brighter than the lobes at either end of the planetary. These lobes look something like ears or handles on a Dutch oven.
Layout, design & revisions © W. D. Ferris
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Revised: October 4, 2005 [WDF]