Built a Pinhole Eclipse Viewer (141/366)

“Three things cannot be long hidden: the sun, the moon, and the truth.”
~ Buddha

Today, there was an annular eclipse of the sun – this happens when the moon is in the direct path between the sun and the earth, but it is not close enough to the sun to completely block the sun’s light (a total eclipse).  The last annular eclipse viewable from the mainland U.S. was in 1994, and we won’t see another one until 2023.

We weren’t in the premium viewing path to see the complete annular eclipse, but we could see part of it – and we were visiting the kids today for a family dinner, so I thought it would be a great time to have some fun with science and make an eclipse viewer.  I’d never done that!

I got instructions from the Exploratorium website (I love that place – we went to one of their “After Dark” events for the first time this year, too!), and though I didn’t have any UPS mailing tubes, I did actually have two large cylindrical tubes lying around, basically just taking up space.  What luck!  And yes, I know I’ve really got to get rid of some stuff …

The instructions said to duct tape the two mailing tubes together – the longer the viewer, the larger the projection.  No problem.  These tubes were about 3 to 4 feet long!

Before I did this though, I cut a viewing hole in one of the tubes – that’s where we’d be able to see our projected image from.  I only needed to cut this hole in one of the tubes since they’d be connected together later.  I thought about using each tube as its own viewer, but I really wanted to get the largest image possible – the instructions noted that the projection would be roughly 1/100th the length of the tube.

The instructions say to cut a hole in one of the ends of the viewer, cover it with aluminum foil, and then make a pinhole in the foil.  I wasn’t sure why they wanted you to make a hole specifically to cover it, and THEN put a pinhole in it, but I thought it might be because the cardboard would be too thick to get a clear pinhole through it.  Since my tubes had plastic caps, I thought I’d try just sticking a pin through the very center of one of the plastic caps for my pinhole.  It seemed to be fine – it was time to test this baby out!

Here’s the Kid anxiously awaiting the results of our eclipse viewer … that’s a total lie – he was probably waiting for his turn with an iPhone or iPad from one of us.  But he’s still just so darn cute.

We went outside to set up our contraption.  Many thanks to my lovely assistants:

It took a little while to find the direct path of rays from the sun – thank goodness there were a few tips on the instructions page – it’s harder than you’d imagine, since the tubes are so long.  Once we had it in the correct placement, voila!

Here’s some time-lapse video from our eclipse viewer experiment.  Because the eclipse happens so slowly (and because there were some adorable rascals inside to hang out with), we didn’t stay outside to watch the eclipse for the entire time – after watching it for a while, I just went outside to shift the viewer periodically so that the image was still there (the moon doesn’t just move in front of and out of the way of the sun – we’re also moving, so the image moved in the viewer as time passed).

This was really cool.  I’m glad we got to do this project as a family – even though this was a pretty simple project, it’s always great to be able to share the magic of nature and science together!

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