Eclipse

Solar Eclipse

Solar Eclipse

August 21, 2017 was a big day for most of the country with a very rare total solar eclipse visible across much of the country.

In Cary, North Carolina, we only achieved about 95% of totality, but it was still an opportunity to test some basic optical principles and photography skills. So I set up a pair of 10x power binoculars as a projector and was pleasently surprised at the details I was able to photograph.

Solar eclipse, first shot

Solar eclipse, first shot

Even from the first photograph, a line of sunspots could be seen across the orb. The gear is nothing special. All of these photographs are of the image projected through the binoculars onto a white piece of paper and are taken with a Nexus 6 smart phone.

About half way to totality, a strange redness in the sky was obvious to several of us observing the event. Despite the short shadows from the midday solar position, the sunlight appeared as if at the end of the day. A significant diminishment of the radiative energy was obvious, too, and everything felt much cooler despite the continued glare.

Solar eclipse at maximum

Solar eclipse at maximum

2:44pm was the maximum pnuembra (shadow) for the photograph above. You can barely see the last sunspot grazing the edge of the moon's edge.

Solar eclipse photography setup

Solar eclipse photography setup

This was a five minute setup. The binoculars were screwed onto a cheap tripod and a large piece of foamcore board was hurridly cut to fit over the objective ends to create a shadow on the observation board. Gentle re-adjustment from time to time re-centered the image to maintain maximum focal clarity. This photo is from early in the event, and we later adjusted it to place the observation board on the ground so the projection was larger and focus more finely adjusted. (The golf umbrella and chair in the background were never used, the event was too exciting to sit down!)

Solar eclipse shadows

Solar eclipse shadows

Shadows during solar eclipses are curious. Tiny openings between the leaves of trees act the same way the binocular setup works and effectively project the sun's image onto the ground. The only difference is that the binoculars use lensees to magnify the image with a short focal length and the tree "pinholes" magnify the images according to the proportion of distance of the hole to the ground.

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Definition: Oriel

Definition: oriel

I bet you say "bay"

More fun with the 2,500 page, unabridged dictionary, without which our literature would be as lost as our architecture...

SUNSET

Blazing in gold, and quenching in purple,
Leaping like leopards in the sky,
Then at the feet of the old horizon
Laying her spotted face to die;
Stooping as low as the oriel window,
Touching the roof, and tinting the barn,
Kissing her bonnet to the meadow-
And the Juggler of Day is gone!

-- Emily Dickinson, 1864
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Definition: Kern

No definition for the structural concept
No definition for the structural concept "kern"
  I recently acquired a 2,500 page, five inch thick, 1975 unabridged Webster's Dictionary. But the massive heft and bulk belie its paucity of architectural information. This dictionary has five entries for kern, but no definitions for the critical structural idea that spanned 1,000 years of architecture and responsible for every stone church in the Middle Ages and Renaissance. The kern is the concept that enabled Dark Ages cathedrals to reach new heights, despite only stone masonry with no ability to resist tensile forces. James Ambrose, in my 1988 structural textbook, Building Structures, defines a kern as "a zone around the centroid of the section within which an eccentric force will not cause tension on the section." Simply put, a kern is the center third of a foundation. When stacking stone, its foundation will resist rotating, lifting a side off of the ground, or cracking in tension as long as the weight and forces of the structure above are within this center third. As soon as forces become eccentric beyond that zone, tension happens. The foundation will want to twist in the ground and additional measures must be taken to avoid a failure. This is easily mitigated with steel today, but before the Industrial Age, builders had to design with the kern to ensure stability. Share: FacebooktwittermailFacebooktwittermail Follow: pinterestrssinstagrampinterestrssinstagram