Sky & Telescope - March 2019 - 56

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 magniﬁcations 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 eastern side through the 130-mm scope at
23×, but at 164× it becomes an attrac-

Targets in the Twins
Object
Castor
NGC 2371/72

Type
Multiple star
Planetary nebula

Mag(v)
1.9, 3.0, 9.8
11.2

Size/Sep
5.3″, 70″

+31° 53′

62′

25.6m

+29° 29′

31.9m

+24° 30′

7h 17.7m

+23° 21′

54″

29.2m

+20° 55′

9′

17.0m

+13° 45′

27.2m

+13° 37′

7h 29.1m

+13° 15′

Carbon star

~8 variable

NGC 2357

Flat galaxy

13.3

4.3′ × 0.4′

NGC 2355
NGC 2395
Abell 21

Planetary nebula
Open cluster

9.9
9.7

Dec.

34.6m

NQ Gem
NGC 2392

RA
7h

Open cluster

8.0

15′

Planetary nebula

10.3

11.3′

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 magnification of the viewing instrument. Right
ascension and declination are for equinox 2000.0.

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 assembly 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 planetary 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 inspiration 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.

NGC 2392: JOE RENZE T TI; SK E TCH: SERG E VIEILL A 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 Vieillard drew this view of NGC 2392 as seen through his 24-inch (620-mm) f/14.5 Cassegrain telescope at a magnification of 1,875×.

Sky & Telescope - March 2019

Table of Contents for the Digital Edition of Sky & Telescope - March 2019