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Southern Cross Constellation
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Southern Cross Constellation
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The main southern cross image is 15 minute exposure on Fujichrome
400, taken in April 1986.
105mm
Nikon lens at f2.8
The stars were tracked using a C5 telescope on an equatorial mount. Otherwise
the stars would be streaks on the picture, due to the earth's rotation.
The simplified southern cross picture is 8 seconds
exposure with a Nikon CoolPix digital camera at maximum sensitivity.
That is not long enough to cause significant streaking at this resolution.
The 1986 lunar eclipse was photographed with a C5 Celestron telescope tracking the moon.
Astrophotography by John Wattie
Pan across the image using arrow keys or scroll bar if you are
using an 800x600 pixel screen
The Southern Cross constellation is
eagerly sought by travellers from the North, visiting the Southern Hemisphere.
The amazing star colours are easily shown on long exposure colour photographs like this,
but are barely recognised by the naked eye, because most stars are too faint to stimulate
colour receptors in our retinas (cones).
The cross has four main stars marking the tips
(alpha, beta, gamma and delta).
These four stars are on the New Zealand flag.
A smaller star (epsilon), separate from the cross, is included on the
Australian flag.
Two bright stars, alpha and beta Centauri, are pointers to the head of the cross.
alpha Centauri is a triple star. It has:
1 and 2) a close double star plus
3) a distant, faint, red star called proxima Centauri.
Proxima centauri is the closest star to our solar system.
The coal sack is a dust cloud,
obscuring stars of the milky way beyond it.
The sack seems black to the naked eye, when seen from a dark sky site.
The coal sack often vanishes behind light pollution over cities.
Southern Cross stars are so bright, they can be seen despite the glare of street lights.
The long exposure photograph is so sensitive, the coal sack has begun to fill in with stars.
The digital photograph only reveals bright stars and is more like what you see
from a city.
Kappa Crucis, to the left (east) of
beta Crucis is not a single star.
It is a star cluster, but at the scale of the main photograph the cluster cannot be resolved.
On the digital image you cannot even see the cluster.
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Moon and Halley's comet pictures
