SunChart Polar Intro

SunChart Polar Intro


All right, and now we got
the same location. Again, the location is going
to be State College Pennsylvania. Solar time is going
to be minus 5 hours, relative to UTC. And latitude longitude
is the same. Again, this is a polar plot of
the same data that you just saw in the previous video. And the north of this plot is
right down at the bottom. The south is up at the top. And I do this in this particular
case, just to keep the arcs in the same
general direction. But you’re going to notice
some differences here. One is that the June arc
is at the bottom. Whereas the December
arc is at the top. So this polar projection is what
you would get if you were effectively lying on the ground
and looking at the sky with a fish eye lens. And then trying to project
that flat. So we see here that we’ve got
the arcs of the day the morning begins over here. The evening ends over here,
right in June time. And the progression of the day
is going to be across the arc, again, from left to right, the
same thing as we had before. Left to right in the winter
months as well. But here you’re really seeing
the differences in the length of the day. It’s probably a lot more
apparent here that the length of the December 21st day is much
shorter of an arc then the summer solstice
on June 21st. Again, our arrows just
pointing out, these green arcs are days. And the red lines are
the hours of the day in solar time. So that this top location here
at 90 degrees, is going to be the top of the sky,
the zenith. So the zenith angle is basically
any angle down from here to one of these circles. Whereas the altitude angle is
going to be the angle up from the ground, which is going
to be in our case the edge of the ring up. So we’re going to see in a
zenith angle going down or going outward, two rings. An altitude angle coming up or
inward, basically coming along the edge of that sky dome. And any one of these points of
these green arcs are going to be a combination of
an altitude angle and a azimuth angle. And here the azimuth angles are
going to rotate from North which is zero degrees. North right here,
is zero degrees. Rotating along to plus 30, plus
60, to finally when we’re due east we are at 90 degrees. When we are do west, we’re
at 270 degrees. South in this case, is going
to be 180 degrees. So the azimuth rotates around
clockwise and 180 degrees is in the meteorological standard
going to south. Again, I want you to pay
attention to the one day of the year when the sun rises due
east and sets due west. And that’s going to be
around this, March 21st through the 23rd. It’s kind of a flexible date
depending on the year. But it basically is defined as
the day when within which the equinox occurs. And so it’s going to be one of
the few days of the only official day that you’re
going to have twelve hours of sunlight. So we can count again one, two,
three, four, five, six hours in the morning, that’s
going to mirror to the six hours in the evening making
it a 12 hour day. And again, that means that we’re
going to have everything in the summer is going to be
longer, whereas everything in the winter months are
going to be shorter. And that’s the flip that I’m
talking about in the notes, that the arcs flip
back and forth. So long days are on the bottom,
short days are on the top, or short days are
towards the south. This should make sense when we
think about the fact that the sun is low in the sky, low in
the sky is going to be closer to the outermost rings. The sun is low in the
sky in the winter. The sun is high in the sky,
especially around the noon hour, during the summer. And you’re seeing that right
here, is that the closer I am to this center ring, the closer
I am to right here. Which is 90 degrees, the higher
in the sky that I am. And so in the winter time, I’m
close to the perimeter, which is close to zero degrees
altitude angle. This up at the top is close to
90 degrees altitude angle.

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