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{{redirect|Bortle|the asteroid|4673 Bortle}} |
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The '''Bortle scale''' is a nine-level numeric scale that measures the [[night sky]]'s [[sky brightness|brightness]] of a particular location. It quantifies the [[astronomy|astronomical]] observability of [[celestial objects]] and the interference caused by [[light pollution]]. [[John E. Bortle]] created the scale and published it in the February 2001 edition of ''[[Sky & Telescope]]'' magazine to help [[amateur astronomers]] evaluate the darkness of an observing site, and secondarily, to compare the darkness of observing sites. The scale ranges from Class 1, the darkest skies available on Earth, through Class 9, inner-city skies. It gives several criteria for each level beyond [[naked-eye]] [[limiting magnitude]] (NELM).<ref>{{cite web|url=http://www.skyandtelescope.com/resources/darksky/3304011.html?page=1&c=y|title=The Bortle Dark-Sky Scale|last=Bortle|first=John E.|date=February 2001|work=[[Sky & Telescope]]|publisher=Sky Publishing Corporation|accessdate=2013-02-20}}</ref> |
The '''Bortle scale''' is a nine-level numeric scale that measures the [[night sky]]'s [[sky brightness|brightness]] of a particular location. It quantifies the [[astronomy|astronomical]] observability of [[celestial objects]] and the interference caused by [[light pollution]]. [[John E. Bortle]] created the scale and published it in the February 2001 edition of ''[[Sky & Telescope]]'' magazine to help [[amateur astronomers]] evaluate the darkness of an observing site, and secondarily, to compare the darkness of observing sites. The scale ranges from Class 1, the darkest skies available on Earth, through Class 9, inner-city skies. It gives several criteria for each level beyond [[naked-eye]] [[limiting magnitude]] (NELM).<ref>{{cite web|url=http://www.skyandtelescope.com/resources/darksky/3304011.html?page=1&c=y|title=The Bortle Dark-Sky Scale|last=Bortle|first=John E.|date=February 2001|work=[[Sky & Telescope]]|publisher=Sky Publishing Corporation|accessdate=2013-02-20}}</ref> The accuracy and utility of the scale have been questioned in recent research.<ref>{{cite journal |author=Crumey, Andrew |year=2014 |title=Human Contrast threshold and Astronomical Visibility |url=http://www.mnras.org/content/442/3/2600.abstract?sid=d939bdd3-1f7e-48af-ac79-3b5b52f357f9 |journal=Monthly Notices of the Royal Astronomical Society|volume=442 |issue=3 |pages=2600-2619 |doi=10.1093/mnras/stu992}}</ref> |
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The table below summarizes Bortle's descriptions of the classes. |
The table below summarizes Bortle's descriptions of the classes. |
Revision as of 17:05, 20 July 2014
The Bortle scale is a nine-level numeric scale that measures the night sky's brightness of a particular location. It quantifies the astronomical observability of celestial objects and the interference caused by light pollution. John E. Bortle created the scale and published it in the February 2001 edition of Sky & Telescope magazine to help amateur astronomers evaluate the darkness of an observing site, and secondarily, to compare the darkness of observing sites. The scale ranges from Class 1, the darkest skies available on Earth, through Class 9, inner-city skies. It gives several criteria for each level beyond naked-eye limiting magnitude (NELM).[1] The accuracy and utility of the scale have been questioned in recent research.[2]
The table below summarizes Bortle's descriptions of the classes.
Class | Title | NELM | Description |
---|---|---|---|
1 | Excellent dark-sky site | 7.6–8.0 |
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2 | Typical truly dark site | 7.1–7.5 |
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3 | Rural sky | 6.6–7.0 |
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4 | Rural/suburban transition | 6.1–6.5 |
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5 | Suburban sky | 5.6–6.0 |
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6 | Bright suburban sky | 5.1-5.5 |
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7 | Suburban/urban transition | 4.6–5.0 |
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8 | City sky | 4.1–4.5 |
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9 | Inner-city sky | 4.0 |
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See also
![](http://upload.wikimedia.org/wikipedia/commons/thumb/d/d4/Suburban_night_sky.jpg/250px-Suburban_night_sky.jpg)
- Night sky
- Sky brightness
- Light pollution
- Dark-sky movement
- Amateur astronomy
- Sky & Telescope (S&T)
- International Dark-Sky Association (IDA)
References
- ^ Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Sky Publishing Corporation. Retrieved 2013-02-20.
- ^ Crumey, Andrew (2014). "Human Contrast threshold and Astronomical Visibility". Monthly Notices of the Royal Astronomical Society. 442 (3): 2600–2619. doi:10.1093/mnras/stu992.
External links
![](http://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png)