My first Magazine Sky & Telescope - 03.2019

MARCH 2019 OBSERVING Deep-Sky Wonders 164× the interior sports a beautiful aquamarine color, has dimmer patches around the central star, and is shaped much like a face — wider and ﬂatter at the forehead and narrower at the chin, which points a little east of north. The face is brightest around the rim and surrounded by a wide, bluish fringe. On some images, the brightness variations near the central star resemble facial features, while the fringe looks like the fur of a parka’s hood. In the 15-inch scope at 345×, the encircling fur is round and about 45″ across. On a good night I can vaguely see how the dim areas within might suggest eyes and a mouth, but on one night of exceptional seeing, I was stunned to see NGC 2392 looking very much like those familiar photos when seen through Alex Langoussis’s 24-inch reﬂector at mag- niﬁcations of 914× to 1280×. As seen in the sketch above, Serge Vieillard was treated to even more marvelous detail through Saint-Véran Observatory’s 24-inch Cassegrain at 1875×, a view I’m sure we all covet. On our way to our ﬁnal target, let’s drop in on the open cluster NGC 2355, south of Lambda (λ) Gem. It’s only visible as a moderately faint, hazy patch with a 10th-magnitude star in its east- ern side through the 130-mm scope at 23×, but at 164× it becomes an attrac- Targets in the Twins Object Type Mag(v) Size/Sep RA Dec. Castor Multiple star 1.9, 3.0, 9.8 5.3″, 70″ 7 h 34.6 m +31° 53′ Planetary nebula 11.2 62′ 7 h 25.6 m +29° 29′ NQ Gem Carbon star ~8 variable — 7 h 31.9 m +24° 30′ NGC 2357 Flat galaxy 13.3 4.3′ × 0.4′ 7 h 17.7 m +23° 21′ NGC 2392 Planetary nebula 9.9 54″ 7 h 29.2 m +20° 55′ NGC 2355 Open cluster 9.7 9′ 7 h 17.0 m +13° 45′ NGC 2395 Open cluster 8.0 15′ 7 h 27.2 m +13° 37′ Planetary nebula 10.3 11.3′ 7 h 29.1 m +13° 15′ NGC 2371/72 Abell 21 Angular sizes and separations are from recent catalogs. Visually, an object’s size is often smaller than the cataloged value and varies according to the aperture and magnifi cation of the viewing instrument. Right ascension and declination are for equinox 2000.0. 56 M A RCH 2 019 • SK Y & TELESCOPE tive, rich group of faint to extremely faint stars. The densest concentration resides within the central 5′, while more loosely scattered stars extend the group to about 8′. The 15-inch scope at 216× reveals more than 55 moderately faint to very faint stars in a ragtag assem- bly bridging at least 9′. The bright star gleams yellow-orange. Sweeping eastward from NGC 2355 with the 130-mm scope at 48× brings me to NGC 2395, a 15′ × 10′ loose group of at least 20 faint stars in the shape of a triangle with a stem to the northwest. Sticking an O III ﬁlter in the eyepiece makes the plan- etary nebula Abell 21 materialize 35′ to the southeast in the shape of a fat, 8′ arc concave toward the northwest. The nebula looks very nice with the 15-inch scope and ﬁlter at 79×. The arc is bright in the northeast, pinned by a superimposed star. It dims in the southeast and becomes bright and narrower in the southwest. The wide areas appear vaguely ﬁlamentary. These snaky ﬁlaments are much more obvious on photos and most likely the inspira- tion behind its nickname, the Medusa Nebula, bestowed by Soviet astronomer Boris Vorontsov-Vel’yaminov in 1960. ¢ Contributing Editor SUE FRENCH welcomes your comments at scfrench@ nycap.rr.com. RD p Left: Like NGC 2371/72, the planetary nebula NGC 2392 is bipolar. William Herschel discovered the nebula in 1787, describing it as “A star 9th magnitude with a pretty bright middle, nebulosity equally dispersed all around. A very remarkable phenomenon.” Right: French observer Serge Vieil- lard drew this view of NGC 2392 as seen through his 24-inch (620-mm) f/14.5 Cassegrain telescope at a magnifi cation of 1,875×.

My first Magazine Sky & Telescope - 03.2019 | Seite 58