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Also AR coating. A layer of material of lower refractive index of just the right thickness (1/4 wave) is deposited on the optical surface to be coated. More complex coatings are possible which cover a large wavelength range.
Industry:Astronomy
metalloid element with three forms. The metallic form is the more stable and is bright, silvery, hard and brittle
Industry:Astronomy
1) A measure of how bright a star looks in the sky. The brighter the star, the smaller the apparent magnitude. A star that is one magnitude brighter than another (e.g., +1 versus +2) looks 2.5 times brighter. The brightest star of all, of course, is the Sun, whose apparent magnitude is -26.74, followed by Sirius, whose apparent magnitude is -1.46, Canopus (-0.72), Alpha Centauri (-0.27), Arcturus (-0.04), and Vega (+0.03). Stars of the Big Dipper are fainter, most of them around magnitude +2. On a clear, dark night, the unaided eye can see stars as faint as apparent magnitude +6, and the largest telescopes penetrate to apparent magnitude +30.
2) Measure of the observed brightness of a celestial object as seen from the Earth. It is a function of the star's intrinsic brightness, its distance from the observer, and the amount of absorption by interstellar matter between the star and the observer. The mv, of Sun, -26.5 mag. A sixth-magnitude star is just barely visible to the naked eye.
Industry:Astronomy
a satellite made by humans which is gravitationaly bound and in orbit of a larger physical object
Industry:Astronomy
