Subject: New Years' Night Moonrise Over Mount Hood
From: Daniel Adamo <[email-masked]>
To: ATIG <[email-masked]>
Date: Wed, 03 Jan 2018 23:06:39 -0800

ATIG Members-

One of my favorite archaeoastronomy documentaries is The Mystery of Chaco
Canyon, first aired 3/15/12 on PBS.  This video focuses on the Anasazi, who
mysteriously disappeared from southwestern U.S. settlements circa 1300 A.D.
Among their other astronomical accomplishments, there's evidence the Anasazi
knew the 18-year cycle of the Moon's nodes on the ecliptic plane and its
influence on at what times of the year eclipses fall.  This cycle is known
as the "Saros" (reference https://eclipse.gsfc.nasa.gov/SEsaros/SEsaros.html
for more on this topic).

Since moving to Salem, Oregon 5 years ago, I've been getting more in touch
with the current Saros now that I have a broader horizon than subdivision
living in Houston, Texas afforded.  This Saros has made me wait those 5
years for the Moon to reach a position more than 19.3 degrees north of
Earth's equatorial plane.  That finally happened on 1/1/2018, and it meant a
nearly full Moon would rise over Mt. Hood's south slope as seen from my east
lawn.  These Mt. Hood Moonrises will only get better over the coming decade
or so.  I've attached a sequence of 6 telephoto images I took to record this
event.  You'll make out Mt. Hood in the deepening twilight just left of the
Moon.  Each attached image is named with the local PST at which it was taken
in "h;mm;ss" format.

All manner of distorting atmospheric effects are apparent in the
attachments.  In particular, note in the last image how the Moon's dimension
orthogonal to the horizon is foreshortened by atmospheric refraction, giving
it a "squashed" appearance.  Any extended object near the horizon looks
bigger than when overhead because the human brain weights visual impressions
that way (probably from success in sighting distant prey or predators
throughout our evolution, if I may use the term).  Measurements of the
rising (or setting) Moon unbiased by human psychology show it's actually
smaller in apparent size than at higher elevations because of atmospheric
refraction.

BTW, the full Moon early this month will be followed by another "blue" Moon
January 31st (in U.S. time zones).  This will also be a "super" Moon with
its full phase falling near perigee.  And, nearly a half year after August
21's total solar eclipse, this full Moon will occur during total eclipse
within Earth shadow.  So, the January 31 full Moon is being called a "Super
Blue Blood Moon" (reference
https://www.forbes.com/sites/trevornace/2018/01/02/supermoon-blue-moon-total
-lunar-eclipse-night/#3aefc0cb45b2).  Circumstances for the lunar eclipse,
which aren't optimal for most U.S. locations, may be downloaded at
http://aa.usno.navy.mil/data/docs/eclipse/L2018Jan31.pdf.

-Dan