Hour angle Negative hour angles indicate the time until the next transit across the meridian; an hour angle of zero means the object is on the meridian. Observing the sun from earth, the solar hour angle is an expression of time, expressed in angular measurement, usually degrees, from solar noon. At solar noon the hour angle is 0.000 degree, with the time before solar noon expressed as negative degrees, and the local time after solar noon expressed as positive degrees. For example, at 10:30 AM local apparent time the hour angle is -22.5° (15° per hour times 1.5 hours before noon). The
61 cm Type 90 torpedo 61 cm Type 90 torpedo The 61 cm Type 90 torpedo was a surface-fired torpedo used by the Imperial Japanese Navy during World War II. It was used in the s and in most cruisers, including the , , , and heavy cruisers after refits during the 1930s. It was superseded by the Type 93 oxygen-powered torpedo, commonly called the "Long Lance", as oxygen generating equipment was installed aboard the cruisers. The torpedo was based on a newly developed British Whitehead torpedo. This weapon used a new double-action two-cylinder engine rather than the four-cylinder radial engine used by World War