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The angle is typically measured in degrees from the mark of number 12 clockwise. The time is usually based on a 12-hour clock. A method to solve such problems is to consider the rate of change of the angle in degrees per minute. The hour hand of a normal 12-hour analogue clock turns 360° in 12 hours (720 minutes) or 0.5° per minute.
An article by Brian Tung containing a link to a C program using a more accurate formula than most (particularly at high inclinations and eccentricities). The program can calculate solar declination, Equation of Time, or Analemma; Doing calculations using Ptolemy's geocentric planetary models with a discussion of his E.T. graph
The cosine of the hour angle (cos(h)) is used to calculate the solar zenith angle. At solar noon, h = 0.000 so cos(h) = 1, and before and after solar noon the cos(± h) term = the same value for morning (negative hour angle) or afternoon (positive hour angle), so that the Sun is at the same altitude in the sky at 11:00AM and 1:00PM solar time. [5]
In order to calculate the position line, the time of the sight must be known so that the celestial position i.e. the Greenwich Hour Angle (Celestial Longitude - measured in a westerly direction from Greenwich) and Declination (Celestial Latitude - measured north or south of the equational or celestial equator), of the observed celestial body is ...
One arcsecond is the approximate angle subtended by a U.S. dime coin (18 mm) at a distance of 4 kilometres (about 2.5 mi). [6] An arcsecond is also the angle subtended by an object of diameter 725.27 km at a distance of one astronomical unit, an object of diameter 45 866 916 km at one light-year,
The clock code is a method of mentally computing the sine of an angle between zero and sixty degrees. Pilots sometimes need to do this to estimate the heading correction due to the wind, and sailors may find it useful to do the same thing to allow for the current due to the tides .
SD- Sub-style distance - this is the angle on the dial plate between the foot of the style and the vertical noon line. SH- Sub-style height - this defines the slope of the style. It has no effect on the design of the dial plate. DL- Difference in longitude- in drawing the dial, DL represents the hour/angle (polar angle)Holwell, John (1712).
The slightly longer stellar period is measured as the Earth rotation angle (ERA), formerly the stellar angle. [4] An increase of 360° in the ERA is a full rotation of the Earth. A sidereal day on Earth is approximately 86164.0905 seconds (23 h 56 min 4.0905 s or 23.9344696 h).