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    Re: What is the Longest Lunar Possible?
    From: Frank Reed
    Date: 2013 Jan 21, 13:14 -0800

    Brad, put your snowshoes away. ;-)

    You wrote:
    "Place the sun and moon at the greatest declination towards your position. That should cause them to be at or above your horizon! So in this rare instance, I do think latitude does matter! Your thoughts on this particular point would be appreciated!"

    Declination?? All you need to remember is that the inclination of the Moon's orbit relative to the ecliptic is only about 5.2 degrees. So basically the Moon runs along the ecliptic through the zodiac constellations just like the Sun and the planets. At Full Moon, the angular distance between the Sun is maximum (that's not quite the definition of Full Moon but nearly so). And that angular distance is necessarily somewhere between 174.8 and 180 degrees. So find the Sun in the sky (or estimate where it is below the horizon). It has some altitude and azimuth. Add 180 to the azimuth and then negate the altitude. You will be looking at a spot that is within 5 degrees of the Moon's position. If the Sun is very close to the horizon, then the Full Moon is very close to the horizon. Whether you're in the Arctic or not doesn't matter. It does, however, affect the rate of altitude change. You could have a very long window for such an observation at some special locations and dates. For an extreme example, suppose you're at the North Pole near an equinox (with the Sun still at a couple of degrees northerly Declination) and suppose Full Moon occurs within a day of that date. Starting up to 12 hours before/after the exact time of Full Moon, you would then have hours and hours when the Moon and Sun would both be above the horizon and the lunar distance would be close to 180 degrees.


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