OBSERVING
Deep-Sky Wonders58 March 2014 sky & telescopeeastern end adds a very short handle. This part of IC 433
is called the Jellyfi sh Nebula, because in images it looks
like a jellyfi sh bell and has tentacles of nebulosity trailing
southwest.
IC 443 displays two sections when viewed in my
10-inch scope at 44×, with either a narrowband or an O III
fi lter. The northeastern arc appears brightest. It’s shaped
like a fat parenthesis mark nearly ½°° long, one-third as
wide, and concave toward the southwest. The section
near Eta is much more diffi cult — I can only detect it as
an amorphous patch of light southeast of the star and
perhaps 12′ across.
German astronomer Max Wolf discovered IC 443
and dimmer IC 444 to its east-northeast with a 2¼-inch,
portrait-lens astrograph in 1892.
Not far from IC 443, the probable planetary nebula
Howell-Crisp 1 dwells 1.1° north-northwest of Mu (μ)
Geminorum and only 11 ′ south of the 7.3-magnitude star
HD 44251. I couldn’t spot it with my 14.5-inch refl ector at
276 × — until I added a narrowband fi lter. Then, a little
touch of mist made its debut, resting on the northeastern
wing of a 10′ asterism that resembles a butterfl y. HoCr 1
seems slightly elongated and about 35′′-long, with a very
faint star nuzzling the northeastern end. Knowing what
to expect, I could then detect the nebula using averted
vision with the fi lter removed. In many images, the
nebula looks rather blocky.
Michael Howell discovered HoCr 1 on an image he
made in early 2006. Later that year, he began a collabora-
tion with fellow narrowband-imager Richard Crisp to
identify it. Astronomer George Jacoby provided high-reso-lution images and is listed as the primary investigator in
a 2010 paper in Publications of the Astronomical Society of
Australia that includes this object. Spectral data support
its classifi cation as a planetary nebula.
Finally, we’ll visit the planetary nebula Jonckheere
900. You’ll fi nd it 1.5° due west of the pretty, low-power
double 20 Geminorum, whose components shine yellow
and yellow-white. J900 is easy to see through my 105-mm
refractor at 47×, but it appears stellar. At 122× it becomes
a tiny nebula with a star on its south-southwestern edge.
I tried some intermediate magnifi cations, but star and
nebula blended together as one little blob.
Robert Jonckheere was one of the leading double-star
discoverers of the 20th century. Among his fi nds were
some nebulae and galaxies masquerading as double stars.
In 1912 Jonckheere announced that J900 is a 3′′ planetary
nebula showing two stellar points within. In 1917 Edward
Emerson Barnard wrote that with the 40-inch Yerkes
Observatory refractor, the nebula spanned 7.9′′ and was
possibly a little brighter in the east, but he saw no central
condensation or stars. Jonckheere replied that he’d seen
three condensations in 1915, and he attributes the diff er-
ence in the nebula’s apparent size to the aperture of the
telescopes. His original estimate of 3′′ was made with a
12.8-inch refractor, and his 1915 estimate with a 28-inch
refractor was 6.1′′. The presence of knots in J900’s struc-
ture was later confi rmed photographically. What do you
see through the eyepiece of your telescope? ✦Jonckheere 900HoCr 1HD 44251μ
η
IC 443ESA / HUBBLE / JOSH BARRINGTONPOSS-I / CALTECH / PALOMAR OBSERVATORYDSW layout.indd 58 12/17/13 2:51 PM