Sky & Telescope - February 2020 - 55

in the 105-mm scope and 55 in the
130-mm scope.
If you visualize Collinder 69 as
Orion's head, then the giant is a
pinhead. But Sharpless 2-264, the
6½°-wide emission nebula surrounding
the cluster, gives him a swelled head.
Although Sh 2-264 is quite faint, Lowell
Observatory's Brian Skiff found it
"straightforward" with the unaided eye,
and California amateur Robert Ayers
has spotted it through 7×42 binoculars. Also in California, Kevin Ritschel
observed the nebula with filter-aided
eyes. Ritschel mounted a pair of 2-inch
hydrogen-beta filters in holes cut into
a shallow box, and he held the box up
to his face like a mask. This not only
helped him combat light pollution, but
also kept stray light from reflecting off
the back of the filters.
Sh 2-264 is too big to fit in the field
of my refractors, even at lowest power.
But I've been able to detect the nebula
by sweeping a telescope across it and
watching for edge effects, where the
brightness of the nebula ends and gives
way to a darker, nebula-free background. This works best with a hydrogen-beta filter, but a narrowband nebula
filter can also help.
Collinder 69 is an extremely youthful
cluster - only 5 million years old - and
just 1,400 light-years distant. The clus-

shoulder. Both stars look white through
my 130-mm refractor, the attendant
watching its 4.4-magnitude primary
from the northeast. Separated by only
1.3″, the components are split by a hair
at 164× and nicely split at 234×.
The position of Orion's head is
marked by Lambda (λ) Orionis and the
other bright stars of the loose cluster
Collinder 69. Lambda is a double star
with blue-white, 3.5- and 5.5-magnitude components separated by 4.9″ and
split in my 105-mm refractor at 87×. At
low power, Collinder 69 covers about 1°
and shows about 45 bright to faint stars
ξ

4h 50m
1662

Alessi 29

π2

+10°

Alessi 29

π1

π3
π4

32

+5°

π2

2180

ρ

ORION

π6
2071
M78

ζ
2184

6h 00m

ε
σ

4h 45m

+10°
Elosser 1

γ

Betelgeuse
2186

π1

vdB 38

1

4h 55m
6

1662

Cr 69

φ

α
Star magnitudes

ter and its surrounding nebula are part
of the Orion Complex, a vast array of
nebulae and youthful stars that engulfs
most of the constellation.
Now we'll leap over to a few open
clusters in eastern Orion. The fi rst is
NGC 2186, found two-fifths of the
way from 8 Monocerotis to Betelgeuse.
My 130-mm refractor at 37× displays a small hazy patch flecked with
two stars. At 117× the southern star
becomes a close pair, the northern one
gleams yellow, and a half-dozen faint

ο2
6

λ
φ2

ASTERISM: POSS-II / CA LTECH / STSCI / PA LO M A R OBSERVATORY;
NEBUL A: SE A N WA LK ER / S&T

vdB 37

Sh 2-264

μ

2
3
4
5
6
7

head of Orion and lie at the center of the huge
nebula Sharpless 2-264. Note also the nebulosity around Betelgeuse in the lower-left corner
and the small, bright nebula van den Bergh 38
near the right margin.

ο1

2169
2194

1

p The bright stars of Collinder 69 make up the

Star magnitudes

Elosser 1

π5
ORION

δ

4
5
6
7
8
9
10

+8°

+0°
Elosser 1

η
5h 30m

5h 00m

π3

10
sk yandtelescope.com * FEBRUARY 2 02 0

55


http://www.skyandtelescope.com

Sky & Telescope - February 2020

Table of Contents for the Digital Edition of Sky & Telescope - February 2020

Contents
Sky & Telescope - February 2020 - Cover1
Sky & Telescope - February 2020 - Cover2
Sky & Telescope - February 2020 - 1
Sky & Telescope - February 2020 - Contents
Sky & Telescope - February 2020 - 3
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