Table 4 gives the theoretical sky brightness and polarization? for several locations of the sun and the observer. The values of Table 4 may be scaled linearly from the intensity of the sun to the intensity of the SPS reflections since the irradiance is simply a constant multiplier in all of the intensity expressions. Since Table 4 provides intensity in lumens/ft , a conversion to watts/m is convenient. For the solar spectrum and the sensitivity of the eye, the conversion is closely a factor of 10, that is, 2 2 1 watt/m = 10 lumens/ft . The sky brightness due to the sun can be obtained directly from Table 4 (by interpolation if necessary). The sky brightness caused by some other bright object can be obtained also since the sky brightness values of the sun and object will be in the same rate as that of the intensity of the sun to the bright object. Using this approach is actually only a good approximation to the sky brightness since the derivation of the relationships assume that the source illuminated the entire depth of the atmosphere with parallel light. This is and t is the equivalent total thickness of the atmosphere reduced to kilometers of air at standard temperature and pressure. A sample result may be obtained by using the following values for the variables:
RkJQdWJsaXNoZXIy MTU5NjU0Mg==