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The movement of the observer and Sun’s declination change both distort the idealized parabolic noon-curve shape treated by the noon_curve.xls spreadsheet. The spreadsheet noon_motion.xls accounts for both of these effects assuming a uniform speed (F1) and course (F2) of the vessel for the duration of the procedure. The number of observations goes to cell F4 and the date is entered in cells F6 and F7. All other cells have the same meaning as in the noon_curve.xls spreadsheet with important clarifications. The coordinates of the fix (H9-11 and H16-18) pertain to the vessel’s position at the moment of the last observation; it is this moment for which the declination of the Sun (H3) should be entered. The equation-of-time value (H14 or H15), however, applies to the computed instant of local apparent noon (H13).

Summary for spreadsheet noon_motion.xls:

Input cells: columns A and B, F1, F2, F4, F6, F7, H3, H4, H5, H14, H15, (F14, F15 optional)

Output cells: H9, H10, H11, H16, H17, H18

Intermediate cells: F16, H13