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Published on Jun 7, 2009
This is a demonstration of one of the spreadsheets available from http://www.navigation-spreadsheets.com/. These spreadsheets carry out computations used in celestial navigation. This demo is performed on an iPod Touch; any computer or smartphone with an Excel compatible spreadsheet application will do.
About moon.xls: This spreadsheet calculates Moon's Greenwich Hour Angle (GHA), declination (Dec), semidiameter (SD), horizontal parallax (HP), and phase data. The input is Universal Time (UT) in years, months, days, hours, minutes, and seconds. The GHA and Dec are the coordinates of the Moon's Geographical Position (GP) defined as the location from which Moon appears directly overhead (in zenith). The SD and HP data are needed for corrections to the sextant altitude (Ho), which determines the radius (i.e. zenith distance = 90 - Ho) of the circular line of position centered at the GP.