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  2. Bortle scale - Wikipedia

    en.wikipedia.org/wiki/Bortle_scale

    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 .

  3. Light pollution - Wikipedia

    en.wikipedia.org/wiki/Light_pollution

    The Bortle scale is a nine-level measuring system used to track how much light pollution there is in the sky. A Bortle scale of four or less is required to see the Milky Way whilst one is "pristine", the darkest possible.

  4. John E. Bortle - Wikipedia

    en.wikipedia.org/wiki/John_E._Bortle

    John E. Bortle is an American amateur astronomer. He is best known for creating the Bortle scale to quantify the darkness of the night sky. Bortle has made a special study of comets. He has recorded thousands of observations relating to more than 300 comets. From 1977 until 1994 he authored the monthly '"Comet Digest" in Sky and Telescope magazine.

  5. Eta Carinae - Wikipedia

    en.wikipedia.org/wiki/Eta_Carinae

    As a fourth-magnitude star, Eta Carinae is comfortably visible to the naked eye in all but the most light-polluted skies in inner-city areas according to the Bortle scale. [46] Its brightness has varied over a wide range, from the second-brightest star in the sky for a few days in the 19th century, to well below naked-eye visibility.

  6. V352 Aurigae - Wikipedia

    en.wikipedia.org/wiki/V352_Aurigae

    According to the Bortle scale, it is faintly visible to the naked eye from dark rural skies. The star is located at a distance of approximately 970 light years from the Sun based on parallax , [ 8 ] but is drifting closer with a radial velocity of −7 km/s.

  7. 99 Herculis - Wikipedia

    en.wikipedia.org/wiki/99_Herculis

    This system has an apparent visual magnitude of 5.1, [2] which, according to the Bortle scale, makes it faintly visible to the naked eye from suburban skies. Measurements made with the Hipparcos spacecraft show an annual parallax shift of 0.064″, [ 1 ] corresponding to a physical distance of about 51.0 ly (15.6 pc) from the Sun.

  8. Talk:Bortle scale - Wikipedia

    en.wikipedia.org/wiki/Talk:Bortle_scale

    This scale is widely referred to by various names, including very commonly "Bortle scale". A large number of the instances of "Bortle Dark-Sky Scale" in books are references to Bortle's paper title "Introducing the Bortle Dark-Sky Scale", which is usually but not always capitalized.

  9. Surface brightness - Wikipedia

    en.wikipedia.org/wiki/Surface_brightness

    In visible and infrared astronomy, surface brightness is often quoted on a magnitude scale, in magnitudes per square arcsecond (MPSAS) in a particular filter band or photometric system. Measurement of the surface brightnesses of celestial objects is called surface photometry.