Sky and Telescope - March 2017 - 36

NGC 2301

5 Set your larger binos up on a tripod for NGC 2301. In 8×
×50s, the
cluster is little more than a smudge, but when viewed in stabilized
15×70s, stars will begin to pop. The brightest star in the cluster,
8th-magnitude G8 subgiant TYC 148-2862-1, may be a foreground star,
not true member of the cluster.

NGC 2244

6 The brilliant open cluster NGC 2244 dwells at the center of the
Rosette Nebula, and clouds of dust and gas surround its bright stars.
You'll need dark skies to tease out the nebulosity, but even if light
pollution interferes with your view of the Rosette, the hot, young cluster
never disappoints.

NGC 2264

7 The brighter stars of open cluster NGC 2264 outline the rough form
of a traditional Christmas tree. This cluster is a star-forming region, so its
component stars burn blue and hot, energizing the clouds of nebulosity
surrounding them.

M A R C H 2 0 1 7 * SK Y & TELESCOPE

NGC 2244 is the southwest corner of a 1.5° square whose
other corners are marked by Collinder clusters: Cr 97 to the
northwest, and Cr 106 and Cr 107 to the northeast and
southeast. With keen eyes and dark skies, you may also spot a
ﬁfth cluster, NGC 2252, in the middle of the square.
Just over 5° north-northeast of NGC 2244 lies NGC
2264, the Christmas Tree Cluster. The cluster really does
look like a Christmas tree, about ½° tall, with the tip pointing south. The base is marked by 15 Monocerotis, another O
giant. Spectroscopically, 15 Mon is about as blue as it's possible for a star to be, but the perception of star colors varies
enormously among observers, so have a look for yourself. Like
NGC 2244, NGC 2264 is bound up in a vast ﬁeld of subtle
nebulosity, but you'll need crystalline skies and fanatical dark
adaptation to spot any of it in binoculars or small telescopes.
Three degrees northwest of NGC 2264 is a nice little
Y-shaped asterism, and about 6° further on the same track
you'll ﬁnd Xi (ξ) and Nu (ν) Orionis, either the right hand
or elbow of the Hunter, depending on how the stick ﬁgure is
drawn. If you imagine Xi and Nu Orionis as eyes, you'll ﬁnd
a pretty, boxy little group of stars forming a freckled nose
below and between them. This is NGC 2169, the 37 Cluster,
so named because it seems to spell out the number 37 when
seen through a telescope. The "print" here is too ﬁne to read
through binoculars, so instead look for a symmetrical chain
of six stars arching a degree to the east of the cluster.
After you've had a good look at the cluster and the star
chain, scan just over 2° southeast for the wide binocular
pair of 73 and 74 Orionis. This pair of stars is one of my
favorite cosmic odd couples - pairs of objects that show up
well in the same ﬁeld of view, despite lying at wildly different
distances. The southeastern member of the pair is 74 Orionis,
an F-type yellow-white subgiant. It's only slightly larger than
our own Sun, and lies only 63 light-years away (hello, 1954!).
The other star, 73 Orionis, is another story entirely. It's a
blue-white B giant, seven times the diameter of our sun and
almost 700 times as luminous, lying 1,200 light-years away
(hello, Dark Ages!).
For our last stops we're going 10° north, to Gemini and
the western foot of the western twin. You've probably been
here countless times to look at M35, but don't skip to that
famous cluster just yet. Instead, take a minute and check in
on Cr 89, a beautiful and often-neglected open cluster. It's
2° east-southeast of M35, anchored between the foreground
stars 9 and 12 Geminorum. Cr 89 is a little bigger than M35,
a little more spread out, and a little less bright, but it's an
easy catch and a rewarding view, and most binoculars will
show it in the same ﬁeld as its Messier neighbor.
And that brings us to our last stop, M35 and NGC 2158,
another cosmic odd couple. M35 is big and bright, naked-eye
visible under good conditions, and a stunning object in binoculars or telescopes of all sizes. That's because it's close, only
2,600 light-years away. Close is a relative term here, since the
light we see now left M35 around 600 BC, before the founding of the Roman Republic. NGC 2158 is a tougher catch,

NGC 2301: M A RTIN G ER M A NO; NGC 2244: JEREM Y PERE Z; NGC 226 4: L JUBINKO JOVA NOVIC / CC BY-SA 3.0

Binocular Tour

Sky and Telescope - March 2017

Table of Contents for the Digital Edition of Sky and Telescope - March 2017