tale, n. A narrative of real or imaginary events; a story. fable, n. An entertaining and often oral account of a real or fictitious occurrence. Turkey Tales and Frog Fablesn. A narrative of travels and events, mostly real and sometimes entertaining, of the Turkey and the Frog.
Wednesday, August 2, 2017
Prepping for the Solar Eclipse
We are getting psyched for the Great American Eclipse which is less than three weeks from now--August 21. It is the first total solar eclipse visible from the US since February 1979. We have our eclipse glasses and we are ready! I was not sure whether the glasses in paper frames (most readily available) or the ones in the plastic frames would work best over prescription glasses, so I got both in an all inclusive set I found online from the manufacturer. Good thing I ordered them weeks ago. When I looked for them online this evening at least the plastic frames glasses seem to be sold out.
Bill Nye the Science Guy eclipse glasses
Rather than just waiting to run out and look up into the sky on August 21, I have finally begun to do a little background research to be better prepared.
I have seen lots of maps showing the track of the region of totality, such as the one below.
What I did not realize until recently was how much of the eclipse would be visible at other locations.
I stumbled across an eclipse calculator (https://www.timeanddate.com/eclipse/map/2017-august-21) for calculating the timing and magnitude (the fraction of the angular diameter of the disk of the eclipsed body that is covered by the eclipsing body) of the eclipse as a function of location. For example, in Lewisville it will be a magnitude 0.8065, while in Santa Barbara it will be a magnitude 0.701. The calculator site also shows an animation of what the sun will look like as a function of time at any location. However, I think I can get the idea even with just the magnitude number.
The eclipse calculator site also has a neat animation of the shadow of the moon moving over the earth's surface, although the one shown below from Wikipedia, is not bad. Note the tiny little black dot in the middle of the larger shadow. That is the area of total eclipse.
by A.T. Sinclair - http://eclipse.gsfc.nasa.gov/, Public Domain, https://commons.wikimedia.org/w/index.php?curid=8973106
I find it easier to understand the 2D map showing totality after seeing this type of 3D animation.
Things to watch for in a total eclipse. I was aware in general of what the eclipse will look like and also NOT to look at it directly with the naked eye. We will probably not be trying to do any photography of the eclipse itself since it requires special filters and there is the risk of damaging the sensors in the camera.
However, this page indicated the following neat things to watch for near or during totality:
Shadow bands:
About 1 minute before totality, moving wavy lines of alternating light
and dark can be seen on the ground and along walls. These shadow bands
are the result of Earth’s turbulent atmosphere refracting the last rays
of sunlight.
Diamond ring: Seen about 10 to 15
seconds before and after totality, the solar corona (the outer
atmosphere of the sun) becomes visible; seen together with a single
jewel of light from the sun, this creates a diamond ring effect.
The Sun's corona:
As the diamond ring fades, the Sun's corona becomes more prominent and
is visible as a faint ring of rays surrounding the silhouetted Moon. The
corona is the outermost layer of the Sun’s atmosphere, and it is around
200–300 times hotter than the Sun’s surface. The corona’s temperature
can reach over 1 million °C (1.8 million °F).
Baily's beads:
About 5 seconds before totality, Baily's beads appear. They are little
bead-like blobs of light at the edge of the Moon. They are created
because gaps in the mountains and valleys on the Moon's surface allow
sunlight to pass through in some places but not others.
The Sun's chromosphere:
A lower layer of the Sun’s atmosphere, the chromosphere, gives out a
reddish glow which can only be seen for a few seconds after totality
sets in.
Past eclipses. The only eclipse (partial, not total) that I remember seeing was one in the early 80's. According to the eclipse calculator, that was probably May 30, 1984. According to this site, it was a magnitude 0.83 in Lewisville. I remember looking at it using the glassblower's didymium glasses (apparently not recommended, since not all such glasses are certified) on the front steps of the chem building in Denton. The thing that was so unusual even without totality was the strange nature of the light. That was my first realization that much of the light we routinely see that filters through trees is refocused images of the sun...i.e. think pinhole camera, but it is the tiny spaces among the leaves in the trees that are the "pinholes". During the partial eclipse there were small little crescent images of the sun everywhere. Very weird!
Future eclipses. If disaster strikes, i.e. it is majorly overcast and we do not see the eclipse on August 21, we only need to wait another roughly seven years. On April 8, 2024 there will be another solar eclipse visible in the U.S. and Lewisville will be in the region of totality! Mark your calendars now!
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