The Aboriginals have an excellent knowlege of naked eye astronomy. Without
any telescopes at all, you can observe large dark areas on the Moon
that are now known to have resulted from large objects crashing into it
almost 4 billion years ago,
see nebulas and the dark dust cloud remains of supernovae, five planets,
and from one place on Earth or another you can spot the 88 constellations
- the traditional star patterns along with many other different constellations
known to different groups of people all over the world. Australia compared
to much of the world has dark skies generally except in a few major
cities so is an excellent place to begin.
THE CHANGING SKY
The night sky is constantly changing. If you take some hot drinks and
a deckchair out to settle down and watch the sky for a few hours
you can see in only two hours, the stars that were near the Eastern horizon
rise high overhead, while other constelllations will set in the west.
The Moon rises about 40 minutes later on average, every night, so as
well as its phase differing each time it rises, its position relative to
the stars also differs.
The stars themselves rise about four minutes earlier each night a small
difference that adds up to about an hour every two weeks and a whole
day every year.
GOING OUTSIDE
Although any clear night provides an invitation to go outside and see
what is up, some nights offer special events, such as a lunar eclipse,
when the Moon passes through the Earth's shadow such as this one photographed
by Noel Munford on July
15th 2000.
Meteor
showers (which like eclipses, are also forecast) also provide another reason
for turning off the TV and turning on to the night sky.
FIRST NIGHT OUT
When skywatching for the first time, it is best not to rush outdoors
to begin learning the constellations as they are plotted on Starfinder
charts. Take a deckchair (seasoned star watcher's tip for avioding neckstrain)
and get comforatble.
For the beginner, especially a child, the sky is a great wonder. On
your first night out, try connecting the stars to make your own patterns
and figures. Let your imagination roam. It should be memorable and fun.
The night sky can be full of stories with personal meaning as it was to
our fathers.
ORIENTATION
To observe the stars you need to orientate yourself in time and space.
The simplest way to orientate yourself in space is to find a familiar large
object that doesn't move like a tree or house and use it to reference your
observations of the sky figures which do move. That's why they built Stonehenge.
Otherwise start by finding a point of the compass (N, E, S or W). West
is where the sun is setting, east - 180 degrees the other way, was
where it rose. Point your right hand east and your left to the west, now
you are facing south with the north to your back. The simplest way to orient
yourself in time is to begin each nights observing at dusk ( a time you
can easily find the west also).
THE SOUTH CELESTIAL POLE
The North and South Poles are the pivots around which Earth rotates,
and around which the stars appear to be turning. Imagine the earth is a
big marble suspended inside an inflated balloon that is covered in stars.
Keep the balloon still and start rotating the marble. If you were an ant
on the marble facing south and the stars look like they rotate clockwise,
face north and they look like they rotate counter clockwise around these
'celestial poles'. David Malin
took a time lapse photograph centred on the south celestial pole to show
this apparent movement as star trails. If you drop a line from this point
to the horizon you will be facing due South.
As we move away from the Equator to the south, the South Celestial Pole rises higher in the sky and Polaris ( the star that marks the north celestial pole ) disappears beneath the horizon. We calculate latitude by measuring the angle of the South Celestial Pole from the horizon. Different constellations are visible at different latitudes.
Finding the south celestial pole using The Southern
Cross
The Southern Cross, together with the two pointers Alpha and
Beta Centauri will help to find South if you draw an imaginary line from
Gamma Crux through to Alpha Crux, and follow this line through the sky.
Of course, you have to know when to stop. You join the two pointer stars
with a line, divide this line in half, then at right angles draw another
imaginary line through the sky until it meets the line from the Southern
Cross. This point is the South Celestial Pole.
SECOND METHOD: Canopus and Achernar
The second method uses Canopus (the second brightest star
in the sky) and Achernar. Make a large equilateral triangle using these
stars for two of the corners. The third imaginary corner will be the South
Celestial Pole.
THIRD METHOD: The Magellanic Clouds
References and Reading:
A Nature Comapnay Guide - Skywatching by David H. Levy
"Spirits Of The Night Sky" by Laksar Burrra
Pictures courtesy of ©
Anglo-Australian Observatory and Noel
Munford.
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