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Partial (Not Total) Lunar Eclipse - April 4

Discussion in 'Off Topic' started by Curt Renz, Apr 2, 2015.

  1. Curt Renz

    Curt Renz Active Member

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    There will be a partial (nearly total) lunar eclipse during Saturday 2015 APR 04 (early morning in North America). Only folks in western North America and further west will be able to observe the Moon during maximum obscuration by the Earth’s umbra, which I estimate will be 99.5% of the Moon’s diameter at 12:00 UT (05:00 PDT). Some observers further east, including Chicagoland, will be able to see portions of the initial partial phase of the Moon in the Earth’s umbra.

    I’ve created a graphical preview with data for seven phases of the eclipse. The perspective and posted lunar altitudes are for San Francisco, but the event times will be essentially the same for all observers on the night side of the world as long as adjustments are made relative to PDT (UT-7).

    Link to preview graphic and data: www.CurtRenz.com/moon.html

    Unlike other eclipse sources that assume the Earth’s umbra to be perfectly circular, I take into account the oblate shape of the Earth and the resulting elliptical umbra. Belgian eclipse guru Jean Meeus has written eclipse books in association with NASA’s Fred Espenak. They have the upcoming eclipse listed as total. Meeus replied to me, “Yes, I know that the lunar eclipse of April 2015 may be partial if the oblateness of the umbra is taken into account.”

    Those able to view the eclipse at its maximum may be want to report their opinion of whether the eclipse appears partial or total. Photos and descriptions of the eclipse would be welcome additions to this thread.
     
  2. AudubonB

    AudubonB Mild-mannered Moderator Lord Vetinari*

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    Nice heads-up, Curt! We'll try to have the set-up ready to take photos.

    And just because....well, just because -

    we happened to be in northern England (York) on the morning of 20 March, where the clouds parted just at the right time so that we were treated to the close-to-full SOLAR eclipse (92%)...AND we were at the York Observatory, which had obligingly set up a fine, large reflector screen so we could indirectly view the show. Most partial solar eclipses, as you know, are a dud in that a 50% or 60% or 70% sun is still a very bright source of light and thus provides a negligible amount of ambient light diminution. But at 92%, the overall sky was nicely dimmer and the city birds did shut up and go off to roost. We weren't out in the countryside so didn't see any cows lying down....

    A nice unexpected surprise!
     
  3. Curt Renz

    Curt Renz Active Member

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    Thanks, AudubonB. Nice anecdote.

    Meanwhile, my iconoclastic defiance of eclipse authorities, due to my dubbing this morning’s eclipse partial rather than total, became the subject of a Sky & Telescope article: Saturday’s Lunar Eclipse: Not Total?
     
  4. ecarfan

    ecarfan Well-Known Member

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    I have only a modest knowledge of astronomy, but this morning my wife and I got up at 0450 and enjoyed watching the eclipse from the comfort of our pre-heated Model S while sipping coffee. Tall trees near our house made it necessary for us to drive to a nearby location that offered better viewing.

    I did not consider the eclipse to be 100%. It seemed to me that a very small sliver of light was always visible along the uppermost edge of the moon.

    Kudos to Curt for predicting that.
     
  5. Pilot_51

    Pilot_51 Member

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    #5 Pilot_51, Apr 5, 2015
    Last edited: Apr 5, 2015
    It was a total eclipse, barely. All the light hitting the Moon had to pass through the atmosphere. It was just within the umbra for under 5 minutes, making it the shortest total lunar eclipse since 1529 and until 2155. Umbra, in this context, is the part of the shadow where the Sun would be completely blocked by the Earth, provided there were no atmosphere to refract the light around the surface and toward the Moon.
    April 2015 lunar eclipse - Wikipedia, the free encyclopedia

    Edit:
    Of course I would say that before reading Curt's link, or, well, the actual posts in entirety. :redface:
    Good point about the shape of Earth not being a perfect sphere and not usually considered in the models. Hopefully, after this, we'll get updated models with much better accuracy.
     

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