RSAA News of the Month: March 2004
Coonabarabran Shows the Way
New lights at Coonabarabran No.3 Oval are world beaters
The northwestern NSW town of Coonabarabran is the astronomical capital
of Australia. Siding Spring Observatory,
home to the telescopes of the ANU's Research School of
Astronomy and Astrophysics (RSAA), the Anglo-Australian Observatory, the University of NSW
Automated Patrol Telescope and the Faulkes Telescope Project,
is just 20km west of the town.
Siding Spring is the best site for telescopes in Australia, but its
dark skies face the possible threat of increasing light pollution from
future housing and industrial development in the surrounding
region. Coonabarabran
Shire has just shown the world that lights and observatories can
live together. Their new lights for their No.3 sporting Oval have set
a world standard for such installations.
Playing fields used for night matches need to be brightly and
uniformly lit. Normally this is done by banks of floodlights most of
which spill up to half of their radiance into the sky. In some cases
only half of the light actually hits the ground; the rest is wasted
and helps to produce some of the glow that can be seen over every town
and city. No.3 Oval was lit this way and was definitely not popular
with astronomers. So much of the light shone straight at the
telescopes on Siding Spring that it threw shadows on the dome of the
4m Anglo-Australian
Telescope!
Enter Reg Wilson, director of Sydney-based company Lighting Analysis and Design
and RSAA's consultant on lighting. Working with astronomers and the
shire, Reg designed a new system of lights that completely satisfy the
requirements of both the astronomers and the users of the oval. The
result is an example to all shires in the region, some of which
contain towns whose lights are clearly visible from Siding Spring. Reg
is presenting the design and results of the project at the
Asia-Pacific and US regional meetings of the International Dark-Sky Association
in March.
The new lights at Coonabarabran's No.3 Oval.
From a distance
(left) the oval is surrounded by darkness, and the light beam is
clearly seen to be directed downwards.
The oval itself is
brightly and uniformly lit (right), but the individual lights are
not much brighter than the full Moon.
Two images showing the spectacular cutoff of lighting around the
oval.
All of the light is directed onto the playing field. None
is scattered upwards or sideways to annoy the neighbours.
Images: Reg Wilson
With the new lights, no light is wasted. All of the light is directed
downward onto the oval. The lights are spaced to give uniform
illumination across the field and are aimed so that the light cuts off
just outside the fence of the oval. No longer does light shine on the
telescopes whenever a night game is in progress; in fact the lights
are next to invisible from the observatory.
This "World's Best Practice" lighting installation is a real
sign of hope in the struggle to keep the sky dark in the Siding Spring
region. It shows that astronomers and local communities can work
together to solve conflicting requirements with no loss to either
side. The good news for players and the shire is that the new lights
give around 70% more light for the same power usage and the shire's
power bill is less.
Sensible lighting like this is something that will be considered as
Canberra expands to surround Stromlo. RSAA and the ACT Planning and Land
Authority are working together on the problem. With lights that
keep the light on the ground, where it is needed, and telescopes
designed for projects that avoid the worst of any scattered light,
Canberra and Stromlo can grow together to the benefit of both.
A short-exposure (2 sec) mosaic image of the lights and sky-glow of
Weston Creek as seen from Stromlo.
Note the very bright sportsground lighting right of centre. This is
the type of lighting that the No.3 Oval lights replaced.
Despite
the current lighting, the brighter stars of the Southern Cross and
Centaurus show clearly on this short exposure,
an indication that
with sensible lighting in new suburbs Stromlo and Canberra can happily
co-exist.
Image: Kim Rawlings
For more information on the problem of light pollution worldwide,
visit the websites of:
and the links from these pages.
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