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    Re: Jupiter-Venus angular separation
    From: Frank Reed
    Date: 2022 May 2, 08:47 -0700

    Here's a simulated scenario. You know that the Greenwich date is 2 May 2022, and it's somewhere between 07:00 and 15:00 GMT/UT. You have no chronometer... not even a watch. The Moon is New, so no lunars. You have been dropped in a small boat somewhere on Earth by the producers of that reality TV show "Sextants Are Fun!". You have a very good metal sextant, a basic scientific calculator, and you have data equivalent to the Nautical Almanac tables for today. Can you determine your location by star altitudes and Jupiter-Venus separation? How accurately?

    It's nautical twilight, and sunrise is approaching. Your height of eye is about 15 feet. You observe the altitude of the star Atria in the southern sky. It is 15° 07'. Moments later, looking east you observe the altitude of Venus: 27° 52'. Then you carefully measure the angular distance between Venus and Jupiter. Your sextant has a 7x scope, and you can just make out the small disks of the planets. They look like "dots" rather than star-like points. You superimpose the "dots" to bypass any semi-diameter issues. For the center-to-center angular distance, you find 1° 30.5'. 

    Where are you?? And how sure are you of your position?

    Frank Reed
    Clockwork Mapping / ReedNavigation.com
    Conanicut Island USA


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