Two More Classics

Farther north is NGC 2371/2, a fairly distinct bipolar near Castor and Pollux. As in M76, each of the bright lobes has its own NGC designation. In the Atlanta club's 20-inch with a UHC filter at 260x, I could plainly see two wedge-shaped knots or lobes connected by a thin waist and surrounded by a large, faint common envelope. The central star was quite faint but clearly visible without the filter.

NGC 2440 in Puppis is a remarkable and bizarre object, both photographically and visually. It was discovered by William Herschel in 1790, but its full shape was not resolved until much later. NGC 2440 features an extremely hot central star surrounded by an insanely complex core region and two pairs of lobes extending in different directions. In a sense, it's bi-bipolar. Visually it's a wonderful, bewildering object at high magnifications. My most memorable view of it was at the 1993 Winter Star Party in Vic Menard's 20-inch f/6.2 Dobsonian. At 358x the inner core almost defied description — a chaotic mass of bright jets and dark rifts with two jet-shaped lobes that looked almost like a cosmic water sprinkler. To this day it ranks as one of the most enigmatic objects I've seen.

The Small and Compact

Not all bipolar planetaries are easily resolved in amateur instruments. Some are so small that they only grudgingly yield detail and texture to the trained eye at high power. Jonckhere 320 (J320), Jonckhere 900 (J900), and Minkowski 1-7 (Mink 1-7 or PK189+7.1) are small, have high surface brightnesses, and are relatively young. Balick describes J320 as a "peculiar or early butterfly" bipolar; others have described it as showing two sets of extensions. J900 is another small planetary with an inner bipolar structure. Both have sufficient surface brightness to tolerate high magnifications. Not quite as compact is Mink 1-7, a bright oval disk oriented nearly north-south. All three should be visible in moderate-size instruments, but resolving small structures will require a large aperture and excellent seeing.