Sky and Telescope - March 2018 - 55

j

Star magnitudes

2903

N

a
M44

d

+20°

2
3
4
5
6
7

e

b

/

W

+15°

k

CANCER

s

8

_

j

c
V

R

M67

g

k

+10°
IC 523

t

`

Abell 31
2775

¡
c

t

l
S

b
d

+5°

m

e
f
Abell 33

HYDRA

0°

o2
o1

2974

-5°
M48

_

a

-10°

SUE FRENCH

9h 30m

9h 00m

The star-packed open cluster Messier 67 also resides in Cancer, 1.7° west
of Alpha (α) Cancri. Doug and Janet
Adams shared their experience with this
object as well. Doug says, "It's very easy
to ﬁnd from dark skies with the Pocket
Sky Atlas. You can virtually see every
star plotted with the naked eye - position the scope and boom! You've got it.
Nice, rounded cluster with around 20
stars instantly resolved at low power,
and one orange member very evident.
My wife said it resembled Pacman, and
I could see it once she'd said it. It has
a concave shape to the cluster, as if it's
gobbling stars ahead of it." Also observ-

8h 30m

ing with a small refractor, Ireland's
Kevin Berwick says that M67 "is very
rich and bright, and to the east there's
a very bright star. It's quite compact
and very similar to M37 in many ways.
There's a bright fountain of stars in the
cluster and at the top of the fountain is
a rusty orange star." The cluster teems
with about 80 faint stars spanning 22′
through my 105-mm refractor at 87×.
The conspicuous orange star tacks the
group's northeastern rim, and Berwick's
sparkling fountain might also be fancied as a celestial tree.
A considerably more taxing target,
the 16.2′ planetary nebula Abell 31 lies

p The author captured this view of the planetary nebula NGC 3242, commonly called the
Ghost of Jupiter, with her 10-inch Newtonian
reflector at 308× while observing at the Winter
Star Party in the Florida Keys.

3.0° south-southeast of M67 and 25′
southeast of two colorful stars: orange,
8.5-magnitude HIP 43582 and yellow,
8.6-magnitude HIP 43618. Abell 31 is
dominated by lines of doubly-ionized
oxygen (O III) in its central region.
With the help of an O III ﬁlter, experienced observers under dark skies have
nabbed parts of the interior in scopes
as small as 80 mm in aperture. Despite
this impressive feat, Abell 31 is still no
cakewalk in larger instruments.
After observing with friends, New
York's Joe Bergeron wrote, "I didn't see a
trace of it with my Stowaway [90-mm
refractor], though Jenn Polakis immediately saw something in the correct
location. We then looked with Tom
Polakis's 10-inch f/5.5 at 40× with an
O III ﬁlter. Now we could all barely see
a vague circular glow, about half the
size of the parallelogram of stars with
which it's involved. Quite a challenge."
Steve Amerongen of Australia was
able to detect some detail with his
25-inch scope at 144×, and he describes
Abell 31 as a "very large, diffuse glow;
fairly faint PN, with very ill-deﬁned,
soft edges; subtle mottling is visible
throughout disk; also, the galaxy IC 523
is visible about 21′ (from the center of
the nebula) to the northwest; seeing
was very good but transparency was
average." His view was greatly enhanced
with the use of an O III ﬁlter.
Much easier game, the splashy open
cluster Messier 48 dwells in Hydra,
3.0° south-southeast of the yellow,
sk yandtelescope.com * M A RCH 2 018

55
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Sky and Telescope - March 2018

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