52 AUSTRALIAN SKY & TELESCOPE April 2018
TARGETSorange, 8.5-magnitude HIP 43582 and
yellow, 8.6-magnitude HIP 43618. Abell
31 is dominated by lines of doubly-
ionised 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 with
scopes as small as 80 mm in aperture.
Despite this impressive feat, Abell
31 is still no cakewalk with larger
instruments.
After observing with friends, Joe
Bergeron wrote, “I didn’t see a trace of
it with my [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 was able to detect
some detail with his 75-cm 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 centre 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,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 observing with a small refractor,
Kevin Berwick says that M67 “is very
rich and bright, and to the east there’sa 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 3.0° south-southeast of M67 and
25 ′ southeast of two colourful stars: SUE FRENCHSThe author captured this view of the
planetary nebula NGC 3242, commonly
called the Ghost of Jupiter, with her 25-cm
Newtonian reflector at 308×.Abell 33IC 523_`ba
dg/ kejc8_b¡dfelmo^1o^2tck
tjsaCANCERRVS277529032974M48M44M67Abell 31HYDRA9 h 30 m 9 h 00 m 8 h 30 m+20°+15°+10°+5°0 °–5°–10°Star magnitudes324
5
6
7NW