Eclipse: Camera Obscura Saves Your Eyes
It seems like it was as early as fourth grade in Port Arthur's old DeQueen School that we first learned we weren't the only planet in the solar system, the sun was actually a star and occasionally the moon would swing around and block off some of the sunlight reaching earth in a solar eclipse. Now and then the earth puts itself in the way of the sun and moon and casts a shadow on the moon and creates a lunar eclipse.
Seriously, Do Not Look At This Bare-Eyed
But of the two, Mrs. Hilly warned us that looking directly at a solar eclipse could leave us with serious eye damage or even totally blind. In those days 'welding goggles' were the recommended way of viewing an eclipse, nowadays some companies are selling eclipse viewing glasses that are hopefully dark enough to prevent damage. Of course you can damage your eyes called Solar Retinopathy at any time by letting too much sunlight flood the back of your eyeballs. Eclipse damage happens because people think, 'it's kinda dark so it's ok to look directly at the sun" NO! Here's an article on the condition.
Even with welding goggles or viewing glasses, I'm not one to trust my eyesight to these appliances and will not be looking directly at the sun. Of course, at our latitude we're not getting the full effect, but enough to do damage. That's why I will be building a simple box camera obscura.
Believe It Or Not I Drew This
Since light travels in straight lines, ever notice the image of a car or other object on a wall inside a building passing by outside? That's because the reflected light of the auto came through the window and was projected onto your wall.
Get yourself a cardboard box with one side open. I drew a kind of a guide (I'm no artist) above. Place a piece of white paper on the bottom of the box, and drill a small 1/16" to 1/8" hole in the center on the opposite side from the white paper. Place it on the ground and observe the eclipse by looking at the white paper. The paper will be on the bottom, the hole on the top and the open side of the box facing you.
You'll get a virtual image on the paper that you can photograph if you like. As well, as the sun moves across the sky the image will move across the paper - build one a few days early and test it out. If I actually get off the couch and do build one I'll post a photo of it, the last time I made one was to observe a series of eclipses we had in the early 90's.
NASA has an instructional video (Solar Viewing Projector) on this as well, but their engineer uses a set of binoculars to better focus the image using two pieces of white poster board. If your hole in the top of the box is 'clean' enough your image should be fine.
Update: OK... I realized my hand drawing and written instructions may not have been clear so I got off the couch and made a camera obscura.
See the big hole in the top of the box? It was just the biggest bit I had, the small hole in the BBQ lid is a 1/16th. I will experiment the next few days as the little hole may need to be bigger. I used the plastic lid to get a better cleaner hole for the light to pass through. It's off the cheesy crappy pulled BBQ you buy in the stores. I'm a widowed bachelor that can't cook. Don't judge me.
Now the sun can be seen at the lower left side of the paper. I need more paper for this size box, but you can 'adjust' the image by moving the box.
Here's how the whole thing looks assembled. It's better to position the box so the paper is somewhat shaded to give you a better image of the sun.
I still need to 'clean up' the holes I drilled for a sharper image so I'll be looking around for the exacto knife later on.