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Dark skies in Canberra - steps closer?

The future is looking positive (not bright) in Canberra!

by Craig Collins - Canberra Astronomical Society

Representatives from the ANU (Mt Stromlo Observatory), Australasian Dark Sky Alliance, and the Canberra Astronomical Society (CAS) met in January with ACT Government staff responsible for public lighting, to discuss ways of reducing light pollution from public lighting assets in the Molonglo Valley, and greater Canberra. The Molonglo Valley is a relatively recent urban development adjacent to Mt Stromlo with a current population of around 8,000 people, anticipated to grow to ten times that in the coming decades. The outcome of the meeting was quite positive.

Evidence was provided showing some streetlights may not conform to the Municipal Lighting Standard that applies to the Molonglo Valley. The ACT Government agreed to check all streetlights in the valley for compliance against the standard and replace or adjust those that are found to be non-compliant.

With the rollout of ‘Smart node’ LED lighting across the area, over time it will be possible to dim streetlights on a large scale, reducing power consumption and light output. Options include dimming during peak periods of energy consumption; when traffic movement is reduced after around 10 or 11pm; or even permanently dimming streetlights. The government is in the process of determining what is a safe level to dim the lights to.

The meeting led to a commitment from the government to trial light pollution reducing measures in the Molonglo Valley. The use of programmable dimming of streetlights was seen as an ideal opportunity to prove these concepts, to measure the reduction of light pollution through their implementation.

Following on from this, the ACT Government invited Mt Stromlo and CAS representatives to observe the systematic dimming of around one third, or approximately 800 of the streetlights in the Molonglo Valley. The results were quite dramatic. At around 50% luminosity of those lights dimmed (which translates to around the same energy saving), there was a noticeable reduction in scattered light. Conversion of older style lights to LED’s and retrofitting smart nodes to the remaining LED lights in the valley is dependent on funding and resourcing, but the potential energy savings will assist in making the transition a priority. Over time, it should be possible to dim streetlights across all of Canberra. Due to current technical constraints, LED lights can’t be dimmed below 50% for an extended period.

In an update to our initial meeting, government representatives informed us that maintenance procedures are being revised, and hardware purchased to allow the adjustment of lights, so they are mounted horizontally with ‘cut off aeroscreens’ that prevent light being directed above the horizontal. And existing lights in the Molonglo Valley that appear to not meet the relevant Municipal Lighting Standard will be assessed and adjusted or modified if necessary.

Light pollution reducing strategies, including dimmable streetlights and lights that don’t emit above the horizontal will, over time, be implemented across all the ACT. Hopefully there will be a measurable reduction in light pollution both on Mt Stromlo, and in Canberra back yards. Government representatives responsible for street lighting genuinely want to help to make our night sky darker, at the same time reducing energy consumption.

The future is looking positive (not bright) in Canberra!

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