Recent Examples on the WebTheir sky brightness must routinely be 21.5 magnitudes per square arc second or darker—in comparison, a theoretically perfect dark site would have a brightness of 22, while a city with a very polluted light sky could measure around 16 or 17.—Margaret Osborne, Smithsonian Magazine, 24 Feb. 2023 The night sky brightness must typically be equal to or darker than 21.2 magnitudes per square arc second.—Stacey Leasca, Travel + Leisure, 6 May 2021 Hubble has a diameter of 2.4 meters, which gives a resolution of 0.13 arc second for observations at a one-micron wavelength.—Meredith A. MacGregor, Scientific American, 19 May 2020
These examples are programmatically compiled from various online sources to illustrate current usage of the word 'arc second.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.
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