42 AUSTRALIAN SKY & TELESCOPE May | June 2018
BINOCULAR HIGHLIGHT by Mathew Wedel3242_i+h+44CRATERHYDRA(^5) °
bino
cular view
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GC 3242,theGhostofJupiter(Caldwell59),isaplanetary
nebula—concentricshellsofgasblownoffbyadyingstar,
whichremindedearlyobserversofplanetsinsize,shapeand,in
thiscase,evencolour.Planetarynebulaearemostlysmallanddimas
seen from Earth, and few of them are within reach of binoculars.
NGC3242issmall,about0.7′across,butit’snotdim.Mostsources
giveavisualmagnitudeof7.7forit.InhisbookTheCaldwellObjects,
StephenJamesO’Mearareportedthatat23×through a 100-mm scope,
NGC3242stilllookedbasicallystellar.However,specificallybecause
itslightiscondensedintosuchasmallarea,O’Mearareckonedthatit
oughttobenaked-eyevisibleundersufficientlydarkskies.Ahandful
ofobservershavesinceconfirmedthatpossibility.
Here’syourmission(shouldyouchoosetoacceptit).First,gohave
alookatNGC3242withbinoculars.Imean,youwillseeit.Andeven
ifitjustlookslikeapointoflight,weshouldn’tgettooblaséabout
witnessing the death throes of astaracrossagulfofthousandsof
light-yearswithhandheldinstruments.Second,seeifyoucandetect
thenebulawithyournakedeyes.Othershavedoneit—canyou?If
not,what’sthesmallestinstrumentorleastmagnificationyouneedto
pickitup?Third,ifyou’rerollingwithbigbinosorasmalltelescope,
determinetheleastmagnificationrequiredtoseethenebulaasan
extended, non-stellar object. Finally, assuming you’re up late enough,
swing east and have a look at M27, the Dumbbell Nebula, and see how
they compare.
MATT WEDEL and NGC 3242 are, in the words of Leslie Peltier, making
mutual estimates of each other’s brightness.
Small but fierce
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M25
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M11 M17
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USING THE
STAR CHART
WHEN
Late April 11pm
Early May 10pm
Late May 9pm
Early June 8pm
Late June 7pm
These are standard times.
HOW
Go outside within an hour or so
of a time listed above. Hold the
map out in front of you and turn
it around so the label for the
direction you’re facing (such as
west or northeast) is right-side up.
The curved edge represents the
horizon, and the stars above it on
the map now match the stars in
front of you in the sky. The centre
of the map is the zenith, the point
in the sky directly overhead.
FOR EXAMPLE
Turn the map so the label
“Facing SW” is right-side up.
About a third of the way from
there to the map’s centre is the
brilliant star Canopus. Go out
and look southwest nearly a
third of the way from horizontal
to straight up. There’s Canopus!
NOTE
The map is plotted for 35° south
latitude (for example, Sydney,
Buenos Aires, Cape Town). If
you’re far north of there, stars
in the northern part of the sky
will be higher and stars in the
south lower. Far south of 35°
the reverse is true.
ONLINE
You can get a real-time sky chart
for your location at
skychart.skyandtelescope.com/
skychart.php
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