Friday, December 5, 2008

Sierra la Rana,Texas ....Αστρονομικό χωριό, στο σκοτεινότερο μέρος των ΗΠΑ

the darkest place in USA

Tract sizes range from 10 to 20-acres or more. Our mission is to preserve the Dark Skies for the residents of Sierra la Rana, the McDonald Observatory and the Big Bend Region today and for future generations.

We are adopting lighting restrictions to preserve, protect, and enhance the nighttime use and enjoyment of any and all property at Sierra la Rana; reduce problems created by improperly designed and installed outdoor lighting; and minimize adverse effects on residents, vehicle operators and pedestrians, the natural environment, and astronomical observations;

To encourage “good neighbor” lighting practices and systems that attempt to minimize light trespass and glare from shining onto abutting properties or into street traffic.
The Sierra la Astronomy Village is a designated area of the property with Astronomy Specific Deed Restrictions and Light Pollution Controls to maintain the observational quality of the Astronomy Village.
The common viewing area will double as a wildlife and birding viewing area during the daytime hours.

Read more on the Sierra la Rana web-site

Light pollution,
also known as photopollution or luminous pollution, is excess or obtrusive light created mainly by humans. Among other effects, and like any other form of pollution, it disrupts ecosystems, can cause adverse health effects, obscures the stars for city dwellers, and interferes with astronomical observatories. Light pollution can be construed to fall into two main branches: annoying light that intrudes on an otherwise natural or low light setting and excessive light, generally indoors, that leads to worker discomfort and adverse health effects. Since the early 1980s, a global dark-sky movement has emerged, with concerned people campaigning to reduce the amount of light pollution.

Effect on astronomy
Skyglow reduces the contrast between stars and galaxies in the sky and the sky itself, making it more difficult to detect fainter objects. This is one factor that has caused newer telescopes to be built in increasingly remote areas.
Some astronomers use narrow-band "nebula filters" which only allow specific wavelengths of light commonly seen in nebulae, or broad-band "light pollution filters" which are designed to reduce (but not eliminate) the effects of light pollution by filtering out spectral lines commonly emitted by sodium- and mercury-vapor lamps, thus enhancing contrast and improving the view of dim objects such as galaxies and nebulae.
Unfortunately this affects color perception, so these filters cannot be used to visually estimate variable star brightness, and no filter can match the effectiveness of a dark sky for visual or photographic purposes.
Due to low surface brightness, the visibility of diffuse sky objects such as nebulae and galaxies is affected by light pollution more than are stars. A simple method for estimating the darkness of a location is to look for the Milky Way.
Light trespass can impact observations when stray light enters the tube of the telescope from off-axis, and is reflected from surfaces other than the telescope's mirrors (if any) so that it eventually reaches the eyepiece, causing a glow across the field of view since it has not been focused.
The usual measures to reduce this glare, if reducing the light directly (e.g. by changing one's location or having the light turned off) is not an option, include flocking the telescope tube and accessories to reduce reflection, and putting a light shield (also usable as a dew shield) on the telescope to reduce light entering from angles other than those near the target. In one Italian regional lighting code this effect of stray light is defined as "optical pollution", due to the fact that there is a direct path from the light source to the "optic" - the observer's eye or telescope.

"A journey of a thousand miles must begin with a single step." -- Lao Tzu
Copyright © Demetrios the Traveler


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