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The Bortle dark-sky scale (usually referred to as simply 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 .
Starlight overcast moonless night sky [1] 140 microlux: Venus at brightest [1] 200 microlux: Starlight clear moonless night sky excluding airglow [1] 10 −3: 1 millilux: 2 millilux: Starlight clear moonless night sky including airglow [1] 10 −2: 1 centilux: 1 centilux: Quarter Moon 10 −1: 1 decilux: 2.5 decilux: Full Moon on a clear night ...
Sky Quality Meter model SQM-L. A sky quality meter (SQM) is an instrument used to measure the luminance of the night sky, more specifically the Night Sky Brightness (NSB) at the zenith, with a bandwidth ranging from 390 nm to 600 nm. [1]
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A dark-sky preserve (DSP) is an area, usually surrounding a park or observatory, that restricts or reduces light pollution or maintains and protects naturally dark night skies. Different terms have been used to describe these areas as national organizations and governments have worked independently to create programs.
The dark-sky movement is a campaign to reduce light pollution.The advantages of reducing light pollution include an increased number of stars visible at night, reducing the effects of electric lighting on the environment, improving the well-being, [1] health [2] and safety [3] of people and wildlife, [4] and cutting down on energy usage.
The following diagnostic systems and rating scales are used in psychiatry and clinical psychology. This list is by no means exhaustive or complete. This list is by no means exhaustive or complete. For instance, in the category of depression, there are over two dozen depression rating scales that have been developed in the past eighty years.
The night rating is a prerequisite for the issue of a Commercial Pilot Licence. [4] In Australia, the qualification is known as a "Night VFR rating", and requires 10 hours of flight time at night in an aircraft or simulator, including at least 5 hours of cross-country flight at night in an aircraft. [5] A night rating does not expire. [3] [5]