Sidewalk Astronomy tonight is cancelled, also supermoon demystified

Jane Houston Jones jane at
Sat Nov 12 16:00:45 PST 2016

Hi everyone and welcome new members from the Mojave National Preserve 
star party last weekend!  We are already setting up the spring date 
which we'll announce once its finalized. There were over 50 tents, over 
120 attendees, a couple dozen attendees were urban youth, visiting MNP 
and camping out for probably the first time looking through about 10 
telescopes!  Article and photos

We were expecting a lot of questions about the "Supermoon" at the 
telescopes tonight, but it's super cloudy, so we are cancelling our 
sidewalk astronomy -- we usually hold it near the first quarter moon 
Saturday night, but we did Mojave non that night this month since the 
campground was available. Both Sunday and Monday night will be about 
equally good to measure the "full " or what we astronomers call a 
"perigee" moon, so look in binos

In a nutshell a supermoon new or full moon which occurs with the Moon at 
or near (within 90% of) its closest approach to Earth in a given orbit.  
Dubbed so by an astrologer in 2011. Because the Moon's orbit is an 
ellipse instead of a circle, its distance from Earth varies during the 
month from about 225,800 miles (363,400 km) at perigee, or closest 
approach, to 252,000 miles (405,550 km) at apogee or furthest distance 
in the elliptical orbit. Changing the distance causes the Moon's size 
and brightness to change as well. A perigee moon is on average 7% bigger 
and 16% brighter than an average full Moon, but during an unusually 
close perigee (the supermoon moon), the full Moon can be 12–14% larger 
than a full Moon at apogee (farthest) and 30% brighter. There are nice 
graphics and explanations here --> 

If it is clear tomorrow, the full moon rises at 4:38 p.m. here in 
California. The moon turns precisely full on November 14, 2016 at 1352 
UTC <>. meaning 
the moon will reach the crest of its full phase on November 14 at 1352 
UTC <>. That 
translates to 9:52 a.m. AST, 8:52 a.m. EST, 7:52 a.m. CST, 6:52 a.m. 
MST, 5:52 a.m. PST. The moon will reach perigee – the moon’s closest 
point to Earth for this month – within an one and one-half hours of that 
time.   This EarthSky article gives a lot of other great information and 

There are 4-6 supermoons every year, so have a look, and do what I am 
going to do -- make a moon measuring device and start comparing! All you 
need is an index card shown in the Sky and Telescope magazine article 
above, with some 5 mm to 10 mm slots cut unto it. 6mm is close to 1/4 
inch, fyi.  Hold your moon measurer straight out, aim at the moon, and 
see which slot matches the moon's diameter, write down the date, repeat 
next full moon.  You can also hold your index finger out stretched, and 
see that it covers both regular full moons, closest perigee moons, as 
well as farthest away moons. :-)  Some astronomers hate the name 
Supermoon, but if it raises awareness, I'm good with it. :-)

Jane Houston Jones @jhjones
What's Up November 2016:
Venus, Jupiter and Saturn + more meteor showers

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