Page 66 - Astronomy - October 2017 USA

SECRETSKY

BY S T E P H E N JA M E S O ’ M E A R A

Hello, Moon

Our nearest neighbor in space doesn’t just shine at night.

ost people a sense, biblical: “Let your eyes
associate the look straight ahead; fix your
Sun with day gaze directly before you”
and the Moon (Proverbs 4:25). My gaze
Mwith night — remained relatively focused
and many mythologies tell us forward with occasional
why this is so. But myths are sweeps from side to side.
myths, and perhaps they are I don’t own a smartphone.
the reason why some non- So, I tend to keep my head level
astronomers think that some- as I walk, so that my field of
thing is wrong if they see the vision is partly on the ground The Moon appears above Grand Canyon National Park in this image taken November 9,
Moon during the day. and partly on the sky. 2013. The photographer was backpacking at the time and set up his camera near the
In fact, the Moon is quite Research has shown that if Hermit Rapids area of the Colorado River. WOLFGANG GOLSER
noticeable at various times on we have such a horizontal line
most days throughout its of sight, we see (on average) Hide-and-seek wonder it’s a surprise when
monthly cycle (except for about more Earth than sky: roughly Moon non-astronomers do see it. I
two to three days before or 35° below the horizontal The previous figures suggest once received a call from some-
after New Moon). (Earth), and about 25° above that as we go about our day, we one who feared that the Moon
the horizontal (the sky). My do not see the Moon unless it was going to collide with Earth
Scanners own observations support happens to be within 25° of the because it was near the horizon
Once the Sun rises, humans these figures. We can extend horizon and we happen to be in the daytime.
seem to be naturally pro-
grammed to look (literally) See the light
down and out, but not neces- With only a little thought During the night, there is
sarily up. This is mainly a pro- it becomes apparent just how difficult not much of interest on the
tective mechanism due to the it is to notice the daytime Moon. ground, which under natural
immense brilliance of the solar conditions is swathed in dark-
disk. But up is where you’d have ness. So we look up where
to direct your gaze most of the all manner of celestial lights
time to see the daytime Moon. our sky coverage to approxi- looking in that direction. This caress our eyes.
I tried being a daytime sky- mately 50° by simply rolling usually occurs in the middle We notice the Moon, mainly
watcher for a couple of weeks, our eyes up while keeping a to late afternoon after First because it is the brightest
noting where my vision takes level head, but that probably Quarter and before Full Moon, object in the night sky. During
me naturally throughout the requires a reason to do so, such or in the early to late morning the day, however, the Moon
day. What I discovered was, in as when a bird flitters by. after Full Moon and before hands over its crown to the Sun
Last Quarter. and then gracefully slips into
Around these times, the the background.
Moon is also at or near its If you happen to notice the
brightest (between magnitudes Moon in a blue sky while
–10 and –13), so you’re more you’re with other people, ask
likely to notice it. Add possible them if they’ve noticed it today.
horizon obstructions such as Then listen to their replies, and
trees and buildings, and the perhaps learn something new
fact that many of us are work- about human perception. As
ing or equally occupied for always, send your thoughts to
large chunks of the day. sjomeara31@gmail.com.
With only a little thought it
becomes apparent just how Stephen James O’Meara
difficult it is to notice the day- is a globe-trotting observer
When the Moon is 1 percent illuminated, as in this image taken May 26, 2017, only who is always looking for the
dedicated amateur astronomers will search for it. At this time, our lone natural satellite time Moon — unless you’re next great celestial event.
was a scant 19.2 hours old and appeared only 15° east of the Sun. CHRIS SCHUR specifically looking for it. No
BROWSE THE “SECRET SKY” ARCHIVE AT www.Astronomy.com/OMeara.

66 ASTRONOMY • OCTOBER 2017