…continuedObserving Nebulae Season by Season
Two Great Summer Planetaries
The Ring Nebula (M57) in Lyra is one of the best-known objects in the summer sky. The Ring differs from most planetaries by the almost perfect sharpness of its outlines, and the completeness of the ring form, in contrast to such objects as the Dumbbell Nebula (see below). Also designated NGC 6720, M57 is easily found halfway between Beta (β) and Gamma (γ) Lyrae. It's oval, 80" by 60", and is of the 9th magnitude visually.
I have probably looked at the Ring Nebula with a greater variety of telescopes than I have at any other heavenly subject. One of my best views came with the 12-inch f/17 Porter turret telescope on Breezy Hill in Springfield, Vermont, the site of the annual Stellafane convention. At 200x the ring was bright, slightly elongated, and of uniform luminosity. An increase to 600x changed the picture dramatically. No longer was the smoke ring evenly bright. Instead, two sides of the ring were made up of curved and twisted streamers. The oval now had pointed ends, and the central region was full of turbulent detail.
The August sky contains many delightful planetary nebulae ephemeral spheres of blue and green gas that float amid the pearly star currents of the Milky Way. Certainly one of the most observed is the Dumbbell Nebula, M27, in Vulpecula. To find it, set your finder on Gamma (γ) Sagittae, the head of the celestial arrow. Sweep about 5° north and you should see an M-shaped pattern of stars composed of 12, 13, 14, 16, and 17 Vulpeculae; this group is more conspicuous to the eye than most star charts lead you to believe. M27 is just ½° south of the M's central star.
I don't believe many observers see the dumbbell shape without having a bad wrench to the imagination. With my 4-inch Clark refractor, a quick look reveals the planetary as two cones with their apexes in contact. After finding the best eyepiece for the evening's sky conditions, and by using averted vision, I usually see the faint nebulosity between the brighter parts of the cones. By gently rocking the telescope back and forth which sets the planetary in motion and helps the eye capture the faintest extensions of light I found the end result is a full circle of light, just as one would expect of a planetary. The luminosity of the interior varies greatly, but the circular outline remains firmly fixed. (For more about the Dumbbell Nebula, see "A Pair of Nice Nebulae.")