A Change to a Homemade Eclipse Viewer
About a week ago, I wrote about an eclipse viewer that I made out of a discarded cardboard box for us to use during our upcoming eclipse. I adapted this old shipping box to become a pinhole projection viewer. The sun is projected through a pinhole and onto a screen at the bottom/back of the box so the person viewing the sun isn't looking directly at the sun but is instead looking at a screen with the sun projected onto it. Actually, the sun in the sky is at the viewer's back so the person isn't even facing toward the sun. There is no getting blinded by the sun using this little homemade viewer.
This little project turned out well. I have a large cutout to peer into the box toward the screen at the opposite end of the box and another cutout to mount a pinhole plate made of black construction paper. Making the pinhole in construction paper made it quick and easy to test different sizes of pinholes. After some experimentation, I sized the pinhole at 1/4 inch and that seemed to work well for this size box.
Near the end of my previous blog entry about this little project I mentioned that, in an effort to improve upon this design, maybe I should try to find a lens that I could mount at the pinhole to help focus everything creating an even better projection of the sun. Pinhole photographs are generally quite blurry and this projection box was no different with its 1/4 inch pinhole. However, if I could get some decent focus with a simple lens that I might have lying around, why not use it? I do have quite a collection of spare lenses leftover from free equipment and other projects so I hoped I had one on hand that would work.
After testing dozens of these leftover lenses, I chose a lens that is called a "close-up lens" to use. I actually had one that worked quite well with the size of box I already used for this project. Adding a lens mounted to this projection box would be far easier than starting the whole project over again to accomodate the need for a different size box so it was extremely lucky that the size of this box was just right for the focal length of this lens
The projection of the sun passing through this lens and the pinhole was a little too bright so I added a neutral density filter to this close-up lens. A neutral density filter is like a pair of sunglasses. They cut down on light. These filters are rated at different strengths and this particular filter halved the amount of light passing through the lens and onto the screen at the back of the box. That seemed to be perfect.
In this first photo, I'm holding the lens in place over the pinhole for testing purposes. I didn't want to permanently mount this lens if it wasn't going to work. It will be easy mounting this to the box. I could simply use more of the same black duct tape that I used on the rest of this box to keep this lens in place. For testing purposes, I was simply holding the lens in place in both photos below which worked better than expected!
This really is a great improvement to this homemade project. What is particularly noteworthy isn't necessarily the amount of the scene that is in focus but that color is easily visible too. The most important characteristic of this homemade solar viewer is that it is completely safe to use during eclipses. Safe solar viewing is mandatory to avoid blindness!
For what it's worth, Sheila was also really impressed with how the sun looked in this safe solar pinhole projection viewer.
I'm still hoping for a lucky break in our typical April weather on the day of the eclipse. Right now, however, the forecast is still calling for solid rain on that day while the preceding and succeeding days are forecast to be overcast. I'm hoping that we get lucky so we can view this once-in-a-lifetime event. Regardless of the forecast, I need to be prepared just in case...
EDIT: I keep coming back to look at this photo of the sun and clouds inside this pinhole projection viewer box because it is such an impressive view! Every time I look at it, I say, "Wow!"
Comments
Post a Comment