Astronomer John Hearnshaw is determined to protect and maintain dark skies from light pollution and believes there should be a nationwide law for it.
His New Zealand Dark Sky Handbook is a manual for people interested in learning more about dark skies protection and the abatement of artificial light at night.
It also promotes Astro-tourism, which is growing globally and New Zealand is seen as a world leader.
Tourists often flock to Lake Tekapo for a view of the starry skies, Professor John Hearnshaw says. Photo: 123RF
Listen to the full interview with John Hershaw here
Professor John Hearnshaw says prior the pandemic, about 150,000 tourists a year were coming to see the night sky at the Mackenzie region, which was the first in New Zealand to be recognised in the International Dark Sky Reserve.
"Aoraki Mackenzie was in 2012, then we've had Great Barrier Island followed by Stewart Island and there's a dark sky part called Wai-iti Reserve, just south of Nelson," Prof Hearnshaw says.
"By the end of this year, there are likely to be six or seven and probably a dozen in a few years' time."
Astro-tourism brought in economic benefits for the Mackenzie District, which saw tourists spend about $1 million a day in Tekapo in 2019, he says.
"Certainly a dark sky can be very beautiful and astro-tourists who have come from polluted cities of China, Japan, Korea and many other places in the world, they come to New Zealand to see a really beautiful dark night sky and the milky way, especially in winter, is a fantastic sight in places like Tekapo.
"Too much tourism anywhere can be a bad thing, and New Zealand has to be very careful to control the number of tourists coming here once the pandemic is over."
He hopes his book will help train dark sky guides and anyone wanting to learn more, not just about astronomy, but the legal aspect, economic benefits, tourism, physiology, ecology and aesthetics of the night sky.
"There's a whole lot about lighting ordinances, and what to look at through a small telescope and quite a lot of scientific material on the nature of light and how to measure it.
"One of the fascinations of dark sky protection is that there's so many different topics that come into it and I learned lots of new things myself in writing this book."
The skies above Stewart Island have seen the area classified as 'Dark Sky Sanctuary'. Photo: Supplied / Sandra Whipp
Other areas looking to achieve the dark sky status are in Kaikōura, Martinborough, Fiordland, and Coromandel, he says.
In order to be accredited by the International Dark Sky Association, the place requires a legal protection so that lighting is controlled and to prevent people from shining lights upwards.
"So the key thing is a lighting ordinance should specify that lights are shining downwards onto the ground where a scene needs to illuminated, usually for safety at night... and people can't shine search lights into the sky," Prof Hearnshaw says.
"Illumination of buildings is strongly discouraged or even banned, and ideally the amount of blue light via any outside light is very small because ... it's the blue light that scatters in the atmosphere the most and which is most harmful to human health."
For the Mackenzie District, the council is considering a new clause that will ask people to not shine lights outside their homes, meaning they must pull their blinds or curtains down at night, he says.
Astronomers were among the first to campaign against light pollution, but concerns now have spread to the general public, Prof Hearnshaw says.
"In the last 10-15 years, it's been realised that light pollution at night, especially blue light at night, is very bad for human health.
"Light pollution at night is a major factor in urban environments, it's not just remote country areas, which are probably the darkest ... and we know that light pollution disrupts hormone production."
On the other hand, there are some hormonal benefits to blue light during the day, so it needed to come at the right time, he says.
He believes New Zealand should have a nationwide law on light pollution and controlling blue light.
Another challenge facing the protection of dark skies is the increasing number of near-Earth satellites, he says, describing it as "a total disaster'.
"We're talking about tens of thousands, maybe 100,000 satellites in the next few years, and these are bright objects which totally disrupt the research done by astronomers.
"Astronomers who take images of the night sky studying faint and distant objects often have their pictures completely ruined by satellite trails."
Space companies are trying to be co-operative and some mitigation is possible, he says, but argues it will not be enough.
"It is continuing and the sky will certainly be changed forever if we have 100,000 satellites compared with about 4000 in lower Earth orbit now."
Prof Hearnshaw will be speaking at Create Festival next month.
*John Hearnshaw is an Emeritus Professor of Astronomy at the University of Canterbury, and he has just finished serving as the Vice-President of the International Astronomical Union, which has 12,500 members worldwide