Mississauga Astronomical Society

Thirtysixth Meeting

     Speaker’s’ Night

Day:                Friday, March 11, 2005

Speakers:   Mike Cook

Ian Wheelband

Light Pollution Abatement

Mike and Ian from the Durham Region Astronomical Association, spoke about their work with the City of Oshawa and Durham Region to control light pollution. A view of the Earth from space shows the scope of unwanted light in the night. North America spends $28 billion annually to light up the night sky. Keeping a 100 watt light bulb on 12 hours a day generates 390 kg of carbon dioxide and costs $35 per year. Poor lights mean bad vision and unsafe roads, energy wastage, environmental effects on flora and fauna, and skyglow with loss of our natural heritage. “If not astronomers, then who?” will advocate. There are now good opportunities to advocate because Ontario is asking for initiatives and suggestions for saving energy (see Ontarioconserves.com website). Mike noted that his own site 25 km. north of Whitby has seen its limiting magnitude decrease from 6.2 to 5.8 in about 10 years.

Astronomers are not against night lighting, but advocate for sensible efficient lights that have appropriate fixtures and are energy efficient. Light pollution can be characterized as glare, light trespass, veil luminance, overlighting, up-lighting, and nuisance lighting.

Glare prevents seeing the surroundings at night and is an increasing hazard for drivers and pedestrians especially for aging eyes. Cobra head street light are an especially common cause of glare. Mike pointed out that U of T at Mississauga is badly polluted with this type of lighting. Ideal lighting would allow both central or photopic vision and peripheral or scotopic vision to be used. Full cutoff (FCO) fixtures allow most light to go not over 20 degrees above the horizon and hence avoid glare. Veil luminance prevents the observer from seeing behind the bright light source.  In light trespass, the light spills over to adjacent buildings, bedrooms etc. and is wasted. As a consequence, sleep is interrupted, biologic systems interfered with (e.g. trees changing leaf colour too late in the season). Uplighting such as on ski hills or advertising signs needlessly illuminates the sky. With ratcheting, light is used for purposes other than for safety. Adjacent businesses compete with advertising by trying to outdo each other using bright lights.

In addition to FCO fixtures which direct light only where needed, light bulbs with that use less watts per lumen can be used such as high and low pressure sodium, as opposed to incandescent. Examples of good lighting on a highway and school were shown. Security does not correlate with outdoor lighting as various studies have shown. In fact, glaring light allows criminals to hide in shadows and gives false security and thus less vigilance to the public. Timers, motion sensors and shielding make more sense.

There are success stories. The City of Calgary which is converting 40,000 street lights to FCO designs will save $2 million per year and generate the equivalent of 18,000 tons less carbon dioxide. In Durham Region, the Municipality of Clarington now requires developers to include illumination plans with zero light trespass.

The speakers encouraged us to write to the Ontario Government which is now asking for energy saving ideas. The MAS membership also agreed to form a light-pollution abatement committee.

Sounds of Pulsars

Bob Anderson played recordings of four pulsars. These were PSR BO 329 +54 which pulses at 1.4 per second, the Veil pulsar at 11/sec, Crab pulsar at 30/sec and PSR JC437 -4715 at an incredible 174/sec. The fastest known pulsar rotates at 642/sec.

Submitted by Chris Malicki, Secretary  Chris Malicki, Secretary                               back to M.A.S. meeting reports page
Mississauga Astronomical Society