Sky & Telescope - January 2023 - 32

Undulating Structure
WITCH HEAD IC 2118 is a delightful - but challenging - target that
you'll find in Eridanus just across the border from Orion's blue supergiant
Rigel. The nebula's dust grains reflecting the star's light make it appear
grayish blue (scattering also contributes to this effect).
M43) and a spray of young star clusters. All lie around 1,350
light-years away. Point an 80-mm or larger telescope just
northeast of Zeta (ζ) Orionis (Alnitak) to catch a view of the
Flame Nebula (NGC 2024), a 30′-wide glow bifurcated by a
dark dust lane. About 1° southwest of the center of the Flame
lies the fine multiple star Sigma (σ) Orionis, a gravitationally
bound system of five stars, four of which split nicely in my
85-mm refractor at 133×. About 2.5° northeast of Alnitak,
you'll find the reflection nebulae M78 and NGC 2071, challenging
targets in a small scope even in good conditions.
Orion offers fainter sights for sharp-eyed observers.
About 4° northeast of Alnitak, look for NGC 2112, a
foreground cluster that points the way to the immense
Barnard's Loop. Visual observers can spot the brightest
portions of this emission nebula with binoculars under ideal
conditions. Its 14°-long arc is an easy target for wide-field
imagers. About 1° south of Zeta Orionis you'll come to the
Horsehead Nebula, which consists of the emission nebula
IC 434 and the dark cloud Barnard 33 (the Horsehead itself).
Only larger instruments equipped with a hydrogen-beta filter
and ideal skies will reveal this notoriously difficult object. At
Orion's head, binoculars show the star cluster Collinder 69
and the fine double star Lambda (λ) Orionis. With components
of magnitudes 3.5 and 5.4 separated by 4.3″, Lambda
Orionis splits easily in my 85-mm refractor at 133×. The
Lambda Orionis Nebula, about 5° across, envelops the
cluster and appears in wide-field images of the area, but it's
too faint to spot visually.
32 JANUARY 2023 * SKY & TELESCOPE
SEAGULL IN SPACE IC 2177 is one of those objects that truly seems
to represent its nickname. If you look closely, you'll note that multiple
open clusters, smaller bright nebulae, and dark patches all contribute to
shaping the Seagull.
For wide-field optics, the Radcliffe Wave includes the faint,
smoky Witch Head Nebula (IC 2118), a reflection nebula
that you'll find about 3° west of Rigel in neighboring Eridanus.
It extends northeast-southwest and spans 3° × 1°. This
nebula makes Barnard's Loop seem easy. I've barely glimpsed
it - after considerable effort - on a crystal-clear (but
freezing cold) winter night with my 85-mm refractor and a
35-mm Panoptic eyepiece with a 4° field of view. I saw no
structure, just an ethereal smudge at its brightest section
about 1.2° south-southwest of Beta Eridani.
Monoceros and Canis Major present an oblique glance
towards the eastern end of the Radcliffe Wave. About 2,900
light-years away, the giant Monoceros R2 molecular cloud
emerges into view at NGC 2170, a small reflection nebula
some 1.5° west of Gamma (γ) Monocerotis. Just 2′ across,
this featureless glow is within reach of a 6-inch reflector.
And so we come to our last stop on the Radcliffe Wave,
the Seagull Nebula (IC 2177). It's a large and faint emission
nebula that lies 4,050 light-years away embedded in the Canis
Major OB 1 cloud and is a favorite of imagers. Visual observers
can spot it with a telescope that captures its 20′ × 20′ size.
I've only been able to glimpse it in my 10-inch Dobsonian at
35× with a UHC filter in black skies.
As you've seen on this tour, there's still plenty to see along
the Radcliffe Wave's 8,800-light-year length. Perhaps most
remarkable is the physical connection among the many deepsky
sights along the Wave. The North America Nebula, the
Taurus Molecular Cloud, and the bright nebulae of Orion and
IC 2118: RAINER SPARENBERG / STEFAN BINNEWIES / CAPELLA OBSERVATORY;
IC 2177: STEFAN BINNEWIES / RAINER SPARENBERG / CAPELLA OBSERVATORY

Sky & Telescope - January 2023

Table of Contents for the Digital Edition of Sky & Telescope - January 2023

Contents
Sky & Telescope - January 2023 - Cover1
Sky & Telescope - January 2023 - Cover2
Sky & Telescope - January 2023 - 1
Sky & Telescope - January 2023 - Contents
Sky & Telescope - January 2023 - 3
Sky & Telescope - January 2023 - 4
Sky & Telescope - January 2023 - 5
Sky & Telescope - January 2023 - 6
Sky & Telescope - January 2023 - 7
Sky & Telescope - January 2023 - 8
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Sky & Telescope - January 2023 - Cover3
Sky & Telescope - January 2023 - Cover4
Sky & Telescope - January 2023 - SA1
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