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    Re: Lunar eclipse this Sunday!
    From: Frank Reed
    Date: 2015 Sep 24, 21:16 -0700

    Alan, you wrote:
    "I believe it might be Monday evening, depending on your locale."

    No, it's Sunday night ...in the sense of 'that night which follows Sunday day'. The umbral eclipse begins with a noticeable bite taken out of the Moon at 9:07 pm Eastern Time on Sunday. The period of total eclipse when the Moon is completely immersed in the Earth's shadow lasts from 10:11 pm to 11:23 pm Eastern. And the end of the umbral eclipse, with the last deep dark bite of the Moon re-illuminated, is at 12:27 am, again Eastern Time. Penumbral phases, barely visible, occur before 9:07 and after 12:27. 

    You may be thinking that there is a date issue because that final event occurs in the wee hours of Monday for us east coast observers, but it all starts on Sunday evening for any observers in North America. Just remember, lunar eclipses are visible everywhere at the same absolute time. That shadow is being "painted" on the Moon, and it can't happen at different times except to the extent that we all keep different local time. It's like watching a "simulcast" tv program. This eclipse happens at "9 o'clock, 8 central" just as they say when describing a tv show. For observers watching in western Europe, our 9:07 pm Eastern is, of course, 1:07 GMT so the eclipse begins for them in the small hours of Monday morning. 

    Current weather forecasts look pretty bad for much of the US, by the way, especially in the east. 

    For a celestial navigation enthusiast, perhaps the most interesting thing about this lunar eclipse is that it's happening very close to the "First Point of Aries". The declination of the Moon at the start of the eclipse is near 1° N and the SHA is near 357°, very close to the zero point. That makes sense, of course for a lunar eclipse that happens just a few days after the equinox since the Earth's shadow is directly opposite the Sun on the celestial sphere.

    Frank Reed

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