Solar zenith angle minutes of arc, which is less than the apparent angular radius of the sun. The formula also neglects the effect of atmospheric refraction. Sunset and sunrise occur (approximately) when the zenith angle is 90°, where the hour angle "h" satisfies Precise times of sunset and sunrise occur when the upper limb of the Sun appears, as refracted by the atmosphere, to be on the horizon. A weighted daily average zenith angle, used in computing the local albedo of the Earth, is given by where "Q" is the instantaneous insolation. For example, the solar elevation angle is : An exact calculation
Type 90 Kyū-maru kW (1,500 horsepower). The hydropneumatic suspension units are mounted on the front and rear pair of road wheels, which can be adjusted on-the-fly to deal with uneven terrain, a requirement on Japan's rough, mountainous terrain. According to the Japanese Ministry of Defense official data report, the acceleration of the type is 0–200 m in 20 seconds. The Type 90 has an approximate unit cost of 790 million Japanese yen or approximately 7.4 million US dollars at 2008 exchange rates. 341 Type 90 tanks were produced between 1990 and 2009 with an average annual production number of 19 vehicles. The original