One of the easiest ways to identify the brightness of your night sky is to use the Bortle scale. A light pollution map will show that a large city radiates white to red from the center, and rural areas will appear green to blue.
Where are Bortle 1 locations?
Dark sky preserves, reserves and parks
| Country | Name | Bortle scale |
|---|---|---|
| United Kingdom | Mata ki te Rangi (Eyes To the Sky) | 1 |
| United States | Grand Canyon-Parashant National Monument | |
| United States | Death Valley National Park | |
| United States | Joshua Tree National Park |
What is a Bortle zone?
The Bortle scale (also known as the Bottle 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.
What can you see Bortle 4?
Galaxies become much more attainable at Bortle 4. At Bortle 5 I can see only the brightest galaxies — M81, M82, M31, M101. At Bortle 4, I was able to see M51, its spiral arms, and its NGC companion galaxy. It was one of the few "satisfying" views of galaxies I have had.
Where does the sky glow?
The natural component of sky glow has five sources: sunlight reflected off the moon and earth, faint air glow in the upper atmosphere (a permanent, low-grade aurora), sunlight reflected off interplanetary dust (zodiacal light), starlight scattered in the atmosphere, and background light from faint, unresolved stars and …
What is the darkest spot on Earth?
The measurements revealed the Roque de los Muchachos Observatory as the darkest place on Earth, where artificial light only brightens the night sky by 2 percent.
What is the darkest city in the world?
Using 11 million photometers from 44 of the darkest places, the study concluded that Roque de los Muchachos Observatory, also located in the Canary Islands, is the darkest place on Earth.
What is my Bortle class?
The Bortle scale uses astronomical observations to measure the amount of light pollution for a given location. For example, a Class 1 Bortle sky means that one can observe M33 (Triangulum Galaxy) as a direct-vision naked eye object.
What does Bortle 1 look like?
The sky appears medium- to light gray at the darkest sites on the planet. Even now, at solar minimum, the airglow is often prominent, appearing as very faint, parallel bands that move around slowly throughout the night.
What can I see in Bortle 5?
Bortle Dark Sky Scale
| Number Code | Label | M31 visible? |
|---|---|---|
| 4 | rural/suburban transition | obvious |
| 5 | suburban | easy with direct vision |
| 6 | bright suburban | easy with averted vision |
| 7 | suburban/urban transition | difficult with averted vision |