Light washing the stars out of the sky...

At the beginning of this century, light pollution was not a problem. We didn't even have the term. Air, water and land pollution were not regarded as problems either... But cities expanded and pollution became a problem. Automobiles and industry were poisoning the air and the land. Some "crazy" people raised public awareness about pollution and things were partially solved. In present times companies can lose, and have lost serious money for damaging one's health, intentionally or not. Although it's mainly politics and most politicians don't give a darn on our health, public opinion was apparently strong enough to correct some problems. 

USA is now in a "post industrial" age. Steel mills and coal mines are now closed, cars use lead-free gas and people make computers, create vaccines or trade stocks on the internet. At least some of them.
But the pollution is not gone. We now have something our parents didn't have when they were kids. We now have light pollution, washing the stars of the sky and jeopardizing the future of astronomy and to some extent, science education. 
graphics © Sky and Telescope Magazine 

Light, light everywhere, and nor a drop from stars...

As one can see from the photos below, things have changed around L.A. since 1908. The cities have naturally expanded, but un AVOIDABLE problem came with this expansion. Light escaping from street lamps now make the sky glow and almost nothing can been see in the skies anymore.

Los Angeles CA in 1908, from Mount Wilson Observatory, home of the venerable 100 inches 'Hooker' telescope
1 hour exposure!
photo © KPNO

Los Angeles CA in 1988, from Mount Wilson Observatory
A 10 second exposure would be enough for such a photo.
photo © IDA

A serious problem

In 1988, this is 12 years ago, International Astronomical Union held its colloquium No. 112: Light Pollution, Radio Interference and Space Debris in Washington DC. The conference was sponsored by IAU commission 50 (Identification and Protection of Potential Observatory Sites) and cosponsored by Commission 21 (Light on the Night Sky) and 40 (Radio Astronomy). As always with the IAU symposia, not much has been achieved. The text of the conference has been published by ASP, under ASP conference series, vol.17. The leading professional in the astronomers fight for dark skies is David L. Crawford, professional astronomer at Kitt Peak National Observatories. He edited the above mentioned ASP series colloquium.

Some facts and numbers
Why do astronomers worry? One can always go to the mountaineous deserts in SW USA and build observatories there, right? This is not true anymore. It was true 25 years ago, when the newest major observatory has been built there, Apache Point Observatory.
At the date, ALL major observatories in SW USA are affected by light pollution. Lets look at some pictures and see. 

KPNO, the "prime" inland US observatory
The site is seriously affected by light pollution from nearby Tucson, AZ.
However, AZ light pollution regulations have slowed down the sky brightening
photo © KPNO

The SDSS Survey Telescope at APO The ongoing Sloan Digital Sky Survey is threatened by light pollution from El Paso, TX, 130 miles south. This funny post card from the SDSS Japanese Participation Group clearly show the light "mushroom" of El Paso, straight South of APO. 
photo © JPG

Rising Centaurus over APO
Light from El Paso, TX, 130 miles away, reflects on low altitude clouds in this photo of Centaurus taken from APO with a 35 mm camera and 400 ISO film. 15 sec exposure. 
photo © Alin Tolea

All reasons to be worried

One look at the above photos and one may realize that the skies in SW, though still dark, have all chances to succumb under light pollution in the next decades. And, NO, we cannot rely on space astronomy only. Space astronomy IS cost prohibitive, as shown by the huge cost of the Hubble Space Telescope.

Numbers

Astronomers measure surface brightness (SB) of extended objects, thus the sky, in magnitudes/arcsec2.
The bigger the number, the fainter the object or the darker the sky.
To get an idea, the darkest sky on earth has 22.5 magnitudes/arcsec2. The brightest parts of the Milky way have SB ~ 19.5 magnitudes/arcsec2. Most nebulae and outer part of galaxies have SB fainter that 21 magnitudes/arcsec2.
IF the sky gets brighter than the above numbers, the eye cannot perceive them anymore due to the lack of contrast. But you might think, astronomers use sophisticated detectors, CCD cameras and they can get to objects as faint as 1% of the sky background. This is only 5 magnitudes fainter than the sky.
IF THE SKY IS BRIGHT, there nothing you can do, even with good detectors and large telescopes.
Let's take a look and see how bright the skies are at some SW observatories.

Sky brightness at SW US observatories (1990 levels)
Observatory SB (V)
Mount Wilson 19.0, no Milky Way!!
Mount Palomar 20.5
Kitt Peak 21.5
APO ?-see photo

The source of the above night sky levels is light coming mainly from large cities, away from the site. The sky is brighter toward the city and darker in rest.
Sky brightness is estimated is estimated to increase by about  one magnitudes/arcsec2 / per decade.
However a small local development can destroy the sky much faster. For example, the city of Cloudcroft, NM is only 18 miles north of APO. The street lamps there have no shielding whatsoever and most of them are HPHg(!) a common thing for a small, resourceless city. Future development of this small city could potentially destroy the APO observing site but nobody seems to give a darn... in 1983 Berry (Berry, R., Comm. Int Amateur Professional Photoelectric Photometry, no 9,10) estimated "Escape Distances" from the cities. He are are his numbers, at the 1983 Light Pollution level:

Soon, there will be enough small cities anywhere to threaten every major observing site.

Unfortunately, most professional astronomers have done little or nothing in the fight against light pollution, or at least, nothing that I know of. Except talking. Light Pollution seems to be a TABU subject in the professional astronomy community.
Amateurs are not great either, but there is this small thing that makes me think that amateurs care more about the problem than professional do. In the first place, amateurs make 90% membership of:

IDA and the Amateur Voice

In 1988, David Crawford founded IDA, International Dark Sky Association, the first association to fight against light pollution in US. Although founded by a professional astronomer, it's membership is made 90% by amateurs. You are encouraged to visit their web site for further information about IDA. To quote directly form their web site: 
 
'IDA is growing and now has over 3,300 members from all 50 states and 69 other countries. Of these, about 200 groups have joined as organizational members, including several
astronomy departments, observatories, amateur astronomy clubs, and lighting companies. The AAS and the ASP are members. It is encouraging that over 25 percent of those who
have joined IDA have done so at more than the $30 standard membership level. 

IDA has issued 37 newsletters to date. There have been 153 information sheets produced, as well as other useful handouts. A slide set, illustrating the issues, has been produced
jointly with the Astronomical Society of the Pacific, and it is available from either the ASP or IDA ($25 USA, $30 non-USA), as well as from a number of other sources. IDA has six
supplementary sets of 20 slides each available for those needing additional material ($35 USA each, $40 non USA each; see Information Sheets 15, 16, and 80 for more details). 

IDA has held an Annual Meeting each year since 1988, in Tucson. A number of IDA Sections have also held local and regional meetings, and more of these will be coming regularly in
the future.'
Ever since its inception in 1983, IDA has conducted the fight against light pollution.

 A second, newer US organization is: New England Light Pollution Advisory Group chaired by Harvard Cfa's Daniel Green.
These two organizations are great information resources for light pollution and effective lighting problems. I encourage you to adhere to IDA.
As a recognition of IDA's role in the fight for dark skies, the National Science Foundation has accorded a 150,000 grant to the 11 year old organization. The grant has been accorded on April 27, this year (2000).
There are many organizations worldwide that talk about light pollution now. But public opinion is a hard thing to change... Maybe one day....

Results. Light Pollution Legislation

IDA's and light pollution activists goal is to help public and astronomers understand the negative consequences of light pollution and to help enact light pollution legislation(!)

 The state of Arizona is by far the most "vigilant" state in regards to light pollution, mainly due to the presence of a large number of astronomical observatories there. Beginning 1958, may Arizona communities have enacted light pollution legislation. Pima County, AZ has to the date the best and most restrictive light pollution legislation in US. Tucson has light ordinances too. And legislation works! The sky brightening speed at KPNO has slowed down to half the expected value.
Dozens of small and large communities in US have light pollution legislation now, including San Diego and Seattle.
For an extensive list of lighting ordinances all over US, I encourage readers to visit IDA's web site. And join IDA!

 The leading amateur publication in the fight against light pollution is Sky & Telescope. The prestigious magazine's Light Pollution Page offers information and articles on the subject and links to Light Pollution related pages.

 I am ending here my set of Light Pollution dedicated pages. And I am ending them the same way I started them. With a set of two pictures.

The night Sky through the glare of an unshileded LPS
photo © IDA

The night Sky, on the background of a LPS lamp, when a rejection filter was applied
photo © IDA

 

  © Alin Tolea 2000