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Computing Sunrise/Sunset with the HP 35s

Posted by Justin Sloan (Honolulu) on 29 Apr 2013, 12:30 a.m.

This is a port of a program originally written for the HP-67 calculator and published as part of HP's Standard Pac. It can calculate the approximate sunrise and sunset time in GMT given a date and any position on earth in lat/lon. One of the goals of the port was to eliminate the need to use multiple labels, to essentially use branching instead of subroutines. I would love to hear your thoughts or suggestion for improvement.

In addition, Register E is used during the program execution. Enter positive values for both the northing and easting.

As an example, to calculate the approximate Sunset on 14 June in Honolulu, Hawai'i, you would press the following keys: 14, STO A, 6, STO B, 21.30, STO C, 157.85, STO D, GTO S001, R/S, 1, R/S.

The answer should be 5.12, meaning 0512hrs (5:12am) GMT. This would be 1912hrs (7:12pm) local HST, since HST is -10 from GMT.


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