Light Pollution by Carol Botha

Carol Botha is a member of ASSA (Cape Centre) and also of the Orion Observation Group (OOG).  She is also an accomplished Deep-sky observer and can regularly be found lurking in dark places with her telescope, appropriately cloaked (Ninja-style). Carol is also an active campaigner against light pollution which, for obvious reasons, is an absolute pain in the posterior for astronomers . She also touches on the role light pollution plays in crime prevention and energy wastage.  Cities are often identified as the main transgressors but there is hardly a town, even the one-horse variety ones, that does not have this problem. A problem which humans are not aware of, but which ongoing  research is showing to be very important, is the environmental effect of light pollution on migratory birds and the disruption it causes in the lives of nocturnal birds, animals and insects.

Here is Carol’s very informative coverage of the subject.

Since the dawn of human history, people have been attracted to the splendour of the night sky. To appreciate and study the universe we need dark skies at night.

The invention of artificial light brought great benefits. Astronomers were among the first to become aware that artificial light also had adverse effects as it became more and more difficult to see the stars in urbanised areas. Satellite images of Earth at night have become a wake-up call of how much artificial light is polluting our environment.

Light pollution has become a global problem and has reached such high levels in certain countries that steps have been taken by various organisations to address the problem.

The International Dark-Sky Association (IDA), an educational, environmental non-profit organisation, was established in 1988 and is dedicated to protecting and preserving the night-time environment and our heritage of dark skies. By registering with or supporting such organisations in large numbers, city planners, lighting engineers and manufacturers might be persuaded to take active steps towards reducing light pollution.

When it comes to alternate and anti-light pollution solutions, South Africa is ahead of most African countries, but lagging far behind developed countries. In an effort to save energy, mercury vapour bulbs in street lights are currently being replaced by high pressure sodium vapour bulbs in cut-off fixtures which comply with international standards. Factors taken into account are cost, luminous efficiency, colour rendering and typical life (hours). The resulting orange sky glow over urbanised areas is of minor importance at this stage.

Excessive and obtrusive lighting interferes with astronomical observatories, is particularly annoying for astronomers affecting their ability to dark adapt, obscures the stars in the night sky for city dwellers, has an adverse effect on human health, poses a threat to wildlife, disrupts ecosystems and is a waste of energy.

Potential sources of light pollution are streetlights, exterior and interior lighting of buildings, floodlights, billboard advertising, illuminated landmarks and illuminated sports stadiums. Industrialised and densely populated areas are affected most severely.

Forms of light pollution include:

Light trespass which occurs when stray light illuminates an area other than that which it was intended for;

Over-illumination is the excessive use of light;

Glare is categorized into blinding glare (which can lead to temporary or permanent visual impairment), disability glare (which can lead to temporary but significant visual impairment), and discomfort glare (which is annoying and irritating; extended periods of exposure can cause fatigue);

Light clutter refers to excessive groupings of lights which can cause confusion or distraction;

Sky glow is caused by the combination of all unshielded, stray and reflected illumination shining up into the sky, which is then redirected back to the ground by the Earth’s atmosphere.

Light pollution can be reduced with available, inexpensive technology. Each of us can contribute towards the preservation of dark skies by installing lights that are efficient and do not create stray or excessive illumination.

(1) Use the lowest intensity light for the desired effect;
(2) Turn lights off using a timer, sensor, or manually when not needed;
(3) Improve lighting fixtures, so that light is directed to where it is needed;
(4) Use energy efficient lamps; and
(5) Evaluate existing lighting plans.

Lighting and crime

Fear of crime is a significant concern when it comes to reducing illumination but dark skies do not mean dark ground. Effective lighting improves night-time visibility, safety and security.

Blinding light impairs night vision. Human eyes take 20–30 minutes to fully adapt to darkness and become much more sensitive.

Bad lighting creates dark shadows where criminals can lurk and could contribute to a less safe environment.

Continuous lighting is actually beneficial to criminals. Installing motion detector security lights not only save energy but are more effective and cause less light pollution if directed downwards.

ASSA Dark Sky Section

Director: Johan Smit [darksky@assa.saao.ac.za]

Local officers:
● Polokwane/Pietersburg/Limpopo: Mrs. Magda Streicher
● Johannesburg/Gauteng: Oleg Toumilovitch
● Durban/Kwazulu Natal: Nigel Wakefield
● Pietermaritzburg/KZN: Jake Alletson

The ASSA Dark Sky Section aims to educate, create awareness, and campaign against the misuse of artificial light. The ongoing loss of the dark night sky is of major concern. The over illumination of cities needs to be addressed and Dark Sky Sites need to be respected, protected and preserved for posterity.