http://www.skyandtelescope.com.au 51by Sue French TARGETSThe Crab and the Water Monster
Hydra and Cancer, once fearsome adversaries of Hercules, adorn our autumn skies.
C
ancer, the Crab, and Hydra,
the Water Monster, are
mythologically tied. They battled
the great hero Hercules during the
second task of his 12 legendary labours,
but the tremendous crab and multi-
headed beast were slain by the mighty
demigod. Their constellations are joined
in the sky as well, with Hydra’s head
resting close beneath Cancer’s legs.
Now well placed for observing in the
evening sky, these foes of Hercules will
be the site of our deep sky explorations.
I very much enjoy the observations
other amateur astronomers send me,
and I’d like to showcase some that have
come my way. Let’s begin in Cancer,which is shown as a Y on the all-sky
chart at the centre of this magazine.
The star at the Y’s fork is called Asellus
Australis, the Southern Donkey, while
the star above it is Asellus Borealis, the
Northern Donkey. In a dark sky, you’ll
see a hazy patch halfway between and
a shade west of these stars. This is the
large and beautiful star cluster Messier
44. It’s sometimes called Praesepe,
the ‘manger’ where the Donkeys feed.
Figuratively, this Latin word also means
a bee’s hive, and M44 is more commonly
known as the Beehive Cluster.
Doug and Janet Adams observed
the Beehive under dark skies. Doug
writes, “I was more impressed with
the naked-eye view! Something I don’t
get from Melbourne is just what aneerie nebulous patch it is. Our view
to the north was partially blocked by
surrounding gum trees, and I didn’t
know what it was until I worked out
what patch of the sky we were looking
at.” He also described the view through
their 101-mm scope: “The telescope
view exploded into a large patch of
bright stars. It was framed well at
23 × in the refractor.” Even my 12× 36
binoculars reveal a swarm of about
20 bright bees, nine of them flying in
a V formation and four tinted yellow-
orange. Fainter members double the
count and spread across 70′.
The star-packed open cluster Messier
67 also resides in Cancer, 1.7° west
of Alpha (α) Cancri. Doug and Janet
shared their experience with this objectSKETCH:
JAAKKO SALORANTA; IMAGE: CHAD QUANDT
SUseanOIIIfiltertosearchfortheextremely
faint, diffuse planetary nebula Abell 31; an
H-beta filter might also help. Even with filters,
this is a challenging object that will require dark
skies and (realistically) at least 20 cm aperture.XIn dark skies, the open star cluster M44
is visible to the naked eye. This image was
produced with a total of 1 hour exposure time
with an f/4.9 astrograph.gWAbell 31M44