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  2. Minute and second of arc - Wikipedia

    en.wikipedia.org/wiki/Minute_and_second_of_arc

    The metric system counterpart of the MOA is the milliradian (mrad or 'mil'), being equal to 1 ⁄ 1000 of the target range, laid out on a circle that has the observer as centre and the target range as radius. The number of milliradians on a full such circle therefore always is equal to 2 × π × 1000, regardless the target range. Therefore, 1 ...

  3. Degree (angle) - Wikipedia

    en.wikipedia.org/wiki/Degree_(angle)

    A degree (in full, a degree of arc, arc degree, or arcdegree), usually denoted by ° (the degree symbol), is a measurement of a plane angle in which one full rotation is 360 degrees. [ 4 ] It is not an SI unit —the SI unit of angular measure is the radian —but it is mentioned in the SI brochure as an accepted unit . [ 5 ]

  4. Equation of time - Wikipedia

    en.wikipedia.org/wiki/Equation_of_time

    In the year −2000 (2001 BCE) the May maximum was +12 minutes and a couple seconds while the November maximum was just less than 10 minutes. The secular change is evident when one compares a current graph of the equation of time (see below) with one from 2000 years ago, e.g., one constructed from the data of Ptolemy.

  5. Right ascension - Wikipedia

    en.wikipedia.org/wiki/Right_ascension

    Since a complete circle contains 24 h of right ascension or 360° (degrees of arc), ⁠ 1 / 24 ⁠ of a circle is measured as 1 h of right ascension, or 15°; ⁠ 1 / 1440 ⁠ of a circle is measured as 1 m of right ascension, or 15 minutes of arc (also written as 15′); and ⁠ 1 / 86400 ⁠ of a circle contains 1 s of right ascension, or 15 ...

  6. Angle - Wikipedia

    en.wikipedia.org/wiki/Angle

    An angle equal to ⁠ 1 / 2 ⁠ turn (180° or π radians) is called a straight angle. [10] An angle larger than a straight angle but less than 1 turn (between 180° and 360°) is called a reflex angle. An angle equal to 1 turn (360° or 2 π radians) is called a full angle, complete angle, round angle or perigon.

  7. Solid angle - Wikipedia

    en.wikipedia.org/wiki/Solid_angle

    [1] Solid angles can also be measured in square degrees (1 sr = (180/ π) 2 square degrees), in square arc-minutes and square arc-seconds, or in fractions of the sphere (1 sr = ⁠ 1 / 4 π ⁠ fractional area), also known as spat (1 sp = 4 π sr). In spherical coordinates there is a formula for the differential,

  8. How to watch the Quadrantids, one of the strongest meteor ...

    www.aol.com/watch-quadrantids-first-meteor...

    Maximum meteor activity is expected to peak between 10 a.m. ET to 1 p.m. ET ... And give your eyes about 20 to 30 minutes to adjust to the darkness — without looking at your phone — so the ...

  9. Unit of time - Wikipedia

    en.wikipedia.org/wiki/Unit_of_time

    Ten seconds (one sixth of a minute) minute: 60 s: hectosecond: 100 s: milliday: 1/1000 d (0.001 d) 1.44 minutes, or 86.4 seconds. Also marketed as a ".beat" by the Swatch corporation. moment: 1/40 solar hour (90 s on average) Medieval unit of time used by astronomers to compute astronomical movements, length varies with the season. [4]