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Full Version: predicting lunar eclipses with the HP Prime
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This program predicts the local circumstances of lunar eclipses. The user provides an initial calendar date and a search duration. The geographic coordinates of a user's location are also required in order to compute the topocentric coordinates of the moon at the beginning and end of an eclipse.

The following is the output for an example "hard-wired" in the code. The companion zip archive includes a PDF document that describes the algorithm implemented in this software.

LOCAL CIRCUMSTANCES OF LUNAR ECLIPSES

total lunar eclipse

begin penumbral phase of lunar eclipse

calendar date Jan 21, 2000

UTC time 2 hr 4 min 40.512 sec

julian date 2451564.58658

lunar azimuth angle 83.3338317769 degrees

lunar elevation angle 23.0744073644 degrees

greatest eclipse conditions

calendar date Jan 21, 2000

UTC time 4 hr 45 min 15.84 sec

julian date 2451564.6981

lunar azimuth angle 111.829817885 degrees

lunar elevation angle 52.4267167333 degrees

end penumbral phase of lunar eclipse

calendar date Jan 21, 2000

UTC time 7 hr 25 min 57.216 sec

julian date 2451564.80969

lunar azimuth angle 185.880353341 degrees

lunar elevation angle 69.4308063637 degrees

event duration 5.35464 hours
The attached zip file contains an updated and more accurate lunar eclipse program for the HP Prime. It will take some time to run. It consists of almost 3000 lines of comments and source code.
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