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Shadows is a software package for the calculation and drawing of sundials and astrolabes, available as a freeware in its base level. It has been developed by François Blateyron , software developer and amateur astronomer, who made it available on Internet since 1997 and continues to improve it. [ 1 ]
The Sun is a weakly variable star, and its actual luminosity therefore fluctuates. [3] The major fluctuation is the eleven-year solar cycle (sunspot cycle) that causes a quasi-periodic variation of about ±0.1%. Other variations over the last 200–300 years are thought to be much smaller than this. [4]
Approximate scotopic/mesopic threshold [8] 10 −1: 10 0: cd/m 2: 2 cd/m 2: Floodlit buildings, monuments, and fountains [9] 10 1: 5 cd/m 2: Approximate mesopic/photopic threshold [8] 25 cd/m 2: Typical photographic scene at sunrise or sunset [7] 30 cd/m 2: Green electroluminescent source [5] 10 2: 55 cd/m 2: Standard SMPTE cinema screen ...
For a black body, Planck's law gives: [8] [11] = where (the Intensity or Brightness) is the amount of energy emitted per unit surface area per unit time per unit solid angle and in the frequency range between and +; is the temperature of the black body; is the Planck constant; is frequency; is the speed of light; and is the Boltzmann constant.
Because it is rotating rapidly, approximately once every 16.5 hours, [14] and seen nearly pole-on, its apparent luminosity, calculated assuming it was the same brightness all over, is about 57 times the Sun's. [12] If Vega is variable, then it may be a Delta Scuti type with a period of about 0.107 day. [52]
Redshift is an application that adjusts the computer display's color temperature based upon the time of day. The program is free software , and is intended to reduce eye strain as well as insomnia [ 3 ] (see Sleep#Circadian clock and Phase response curve#Light ).
In 1961 the father-and-son team of Harold and Horace Babcock established that the solar cycle is a spatiotemporal magnetic process unfolding over the Sun as a whole. They observed that the solar surface is magnetized outside of sunspots, that this (weaker) magnetic field is to first order a dipole , and that this dipole undergoes polarity ...
A simple arithmetic calculator was first included with Windows 1.0. [5]In Windows 3.0, a scientific mode was added, which included exponents and roots, logarithms, factorial-based functions, trigonometry (supports radian, degree and gradians angles), base conversions (2, 8, 10, 16), logic operations, statistical functions such as single variable statistics and linear regression.