Sky & Telescope - March 2023 - 32

GARY IMM
Exploring Nebulae in Monoceros
tered on the fantastic emission nebula IC 2177 (also known
as Sh 2-296). Welsh amateur astronomer Isaac Roberts discovered
it photographically in 1898. You'll find it on the border
with Canis Major, about 3° northeast of the Great Dog's nose,
4th-magnitude Theta (θ) Canis Majoris. I paired an O III filter
with my 12-inch Dob and 32-mm Orion Q70 wide-angle
eyepiece to observe this target. For smaller telescopes under a
dark sky, I recommend using wide-field eyepieces and sweeping
the telescope back and forth across the field in order to
tease out the bright nebulae from the dark sky on either side.
Let's start on the western side of this large target by
popping into Canis Major. About 2° northeast of Theta
Canis Majoris, you'll find vdB 88, a large nebulosity around
the 7th-magnitude central star GU Canis Majoris. Now
scan around ½° almost due east for the reflection nebula
NGC 2327. The nebula has a double star comprising 9th- and
12th-magnitude components separated by about 7″ and an
attractive arc of 10th-magnitude stars extending about 4′ to
the northeast. Continuing on a bit more than 1° northeast
to Sh 2-292, a fascinating and complex object displaying
brighter and darker areas centered on the 7th-magnitude blue
variable star V750 Monocerotis. I recommend a hydrogenbeta
filter and a large telescope to fully enjoy this target. Fanshaped
vdB 90 (also cataloged as Parsamian Petrosian 70) is
perhaps one of the stranger objects on this tour - you'll find
it immediately east of 8th-magnitude FZ Canis Majoris. Look
for vdB 92 a bit more than 3′ southeast of 9th-magnitude Z
Canis Majoris. And finally, the northern section of IC 2177 is
32 MARCH 2023 * SKY & TELESCOPE
FAN-SHAPE IN SPACE NGC 2313 (also known as Parsamian
Petrosian 18) comprises the star V565 Monocerotis that illuminates the
cloud of gas and dust visible to its east, with a darker cloud obscuring
the western side of the nebulosity. This combination generates the fan
shape. Astronomers used to refer to objects such as these as cometary
nebulae due to their distinctive shapes, although that term is now
obsolete. Look for this target 9¼° west-northwest of 9th-magnitude SAO
133980, the brighter star at bottom left.
CELESTIAL SEAGULL Straddling the border between Monoceros
and Canis Major, the area around IC 2177 is rich with both bright and
dark nebulae. Use the image at right to guide your observing session.
involved with LDN 1657 and LDN 1658.
Between the two easier regions of NGC 2170 in the west
and IC 2177 in the east we've come across an eclectic collection
of objects offering different levels of difficulty. My
advice: Get out there and observe with whatever instrument
you may have at hand.
¢ RICHARD P. WILDS first viewed southern Monoceros in the
1960s with a 2-inch Tasco, but it took many more years and
different scopes to fully appreciate the region.
FURTHER READING: To learn more about Dobashi dark nebulae
and for links to the catalogs, head to https://is.gd/DobashiK_2005
and https://is.gd/DobashiK_2013. Go to Steve Gottlieb's page
https://is.gd/astronomy_mall to read all about NGC and IC objects.
The table of data for the observing targets discussed here is
at https://is.gd/monoceros_nebulae.
https://www.is.gd/DobashiK_2005 https://www.is.gd/DobashiK_2013 https://www.is.gd/astronomy_mall https://www.is.gd/monoceros_nebulae
Sky & Telescope - March 2023

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