I want to thank Dee for giving me permission to post this here. Not the normal fare for TWW but I suggested to her that she allow something very different and she agreed.
If you have to ask …
When I was in the 5th grade the astronomy bug bit several of us in my neighborhood. This was in rural western KY where we only had to deal with a few street lights in our subdivision. The milky way was easy to see and you could almost read by it. Several of us got telescopes. Mine was $10 from Sears. Refraction vs. reflection was a big debate amongst us then.
As a group one of the first things we wanted to do was stay up so we could see Saturn when it "rose" high enough to see about 2 AM. My mother and a few other parents stayed up with us. After we looked at it though a neighbor's telescope my mother commented how it really took dedication to get up at 2 AM anytime you wanted to study Saturn. We then told her that, well, in a few months it would be visible at 10PM. She, and the other parents, were just a bit flustered and didn't understand why we didn't just wait the few months. Sigh. Sometimes parents, and others, just don't get it.
A project to view and take pictures of the eclipse for minimal cost.
Materials will run between $15 to $30 depending on what you have in your garage. There are pictures at the end.
My goal was to be able to take photos of the eclipse without spending a lot of money and I think I've done it. I started by doing Internet searches for ways that would let me (and the other billion people) use my iPhone's (or that other brand) decent camera to take pictures of the event. I found zip. Now maybe my search ability isn't all that good but I figured the internet would be awash with such things. Oh, well. So here's what I came up with.
In an overly simplistic description I came up with putting two moving boxes together, making a pinhole lens at one end, putting in a nice sheet of white paper inside at the other end, then aiming my phone's camera through a hole next to the pinhole. Been at this evenings for a few days and think I'm done with my 4th iteration.
First was using Lowes small moving boxes and it sort of worked but had multiple drawbacks. My phone mount was very flimsy, my method for the pinhole was tenuous, and the box was awash with reflected light from the image of the sun inside the box. I took a few pics but the sun was a bit fuzzy and not very bright. Light leaking through small holes and cracks in the cardboard joints was also problemmatic. And the option for mounting a FedEx triangular shipping tube was a mess.
So I started on version 2. Same boxes but I ditched the concept of the shipping tube. Just 2 boxes stacked end to end. While thinking about it I started looking into the math and realized that the 30" FedEx tube extension was way too small to allow me to take more than a few minutes pics before the sun would move too far across the sky to still be aligned with my setup. I had put the boxes together, sealed the edges and seams with black Gorilla (duct) tape.
Then I decided to explore the math a bit. Skip ahead of you don't care about these details.
First I wanted to know how big of an image I'd get based on the distance of the pinhole lens from the imaging surface. For this I needed the angular size of the sun. I found two answers. 5.33 and 5.2 degrees. Close enough. If you then do the trig you wind up with an image size that is a bit over 0.1 inch of sun image size per foot of distrance between the pinhole and imaging surface.
Next I wanted to know how long I had for taking pictures and watching the image before moving my box. Taking the sun as moving across the sky (I know. The earth is rotating and this is an illusion …), at 15 degrees per hour. Doing some more trig I came up two talbles. One assuming 10" of imaging surface and another for 16" of imaging surface. This corresponds to an 8.5"x11" of glossy paper in a small Lowes box and 11"x17" of glossy paper in a Lowes medium box.
Taking all of this together a 3' tall box setup using Lowes small boxes would give me roughly 32 minutes of viewing time before I'd need to move my device to keep the image aligned. But a 3' tall box setup using Lowes medium boxes would give me well over an hour of viewing time per box positioning.
With this math behind me I decided to switch to medium boxes. Which meant a trip to Lowes. While I already had the small boxes for use in our home de-cluttering project, the medium boxes were not at hand. Especially not at midnight. Which was about when I finished my math. Or later. (Insert eye roll here by wife.) It has been a few decades since I had to deal with trig at this level.
So version 2 will get re-purposed into packing boxes as originally intended.
Let's digress even more for a minute.
Wikipedia has several good articles on the subject. Between that and some members of a local Mac user group who are retired but helped start the fiber industry in the US I found out some more details. The best pinhole lens is made by putting a 500 nano meter or so perfectly round hole into an infinitely thin, perfectly smooth surface. Well that would blow the budget. So I went for the best I could come up with for $0. I came up with a way to mount a small piece of kitchen grade aluminum foil and poke a tiny hole in it with a pin from a new shirt. Doesn't meet the spec but seems to be good enough. At least it did after some practice gently poking holes into foil. My approach is to take a collection of pieces of foil about 2" on a side, laying them flat onto a semi firm surface, and gently taping them with the pin. I'm open to alternatives but kitchen aluminum foil seems to be the thinest material around that comes close to the perfect option. Anyway back to the box.
Four Lowes Medium boxes plus new supplies of Gorilla tape, packing tape, foam board, and 11×17 glossy paper and I'm ready to start. (Four boxes in case I messed up.) I built one and got a much better sun image than my first box. I had a few issues with the way I cut out the camera and pinhole mounting so I did some thinking and came up with what is now version 4.
So here's what I have.
Take two Lowes medium packing boxes. Fold over the end that does not have the fold downs connected via a cardboard tab. (This makes sense if you see the boxes in person.) Use packing tape to close up the bottom of each box. Keep the box tight and square. Now take the Gorilla tape and tape the open flap edges together. I made the planned bottom box with more of a spread at the edges and the planned top box with the edges tightly together. This would allow me to insert the top box into the bottom box making a larger box. Now make sure that all of the edges, corners, hand hold knockout, etc. are fulling covered by the Gorilla tape to keep out any stray light.
This is optional but painting the inside of the boxes with flat black spray paint should cut down on reflected light washing out the sun image. This took me about 15 to 30 minutes as you want light applications to avoid runs which might create reflecting band inside of the boxes. (Wear a long sleeve shirt and a glove on the hand holding the spray can. You'll understand once you start.)
For this I'm using a piece of 11"x17" glossy printer paper. I've taped it to a piece of foam board to keep it flat and then taped the foam board to the bottom of the box. And, yes, 11"x17" glossy paper is hard to find unless you buy a ream at staples for over $30. But I have clients who have such and a few sheets could be had with permission of course. Putting two 8.5"x11" pieces side by side is the alternative. You will get a small line in your pictures but we're going for a budget of $15 to $30 right?
Foam board mounts
Now take the top box and cut a piece of 1/4" foam board to fit on the top. I'd make it about 1/2" to 1" smaller than the box.
Cut a 1 1/2" to 2" square out of the center of the foam board. Preserve this cutout as one piece that can be put back into the bigger piece. In this small piece cut out a hold about 1/2" in size. Now cut a second small piece of foam board that will fit on top of the first piece cut out of the larger piece. Cut a similar small hole in the middle of this piece. Put packing tape on both to make a surface that wil not peel off. This is your aluminum foil pinhole lens holder. You will be putting your lens between these two and using tape to hold the top piece onto the piece that fits in the larger piece. (Look at the pictures. They will make more sense than this writing.)
Now cut a hole in the cardboard box the same size as the hole in the center of the formboard than lines up with the foam board. Again, look at the pictures.
You now have a pinhole lens that can be removed and replaced as you will likely tear up the foil at times.
Camera (phone) mounting
Line up your phone so the camera lens is close to the pinhole foam cutout but leaving an inch or two for sturdiness. Cut out from the foam a space for your phone to fit snugly into the foam board. Add a cutout so you can plug in your power and ear phones. Now cut out a small hole in the cardboard box directly under your lens.
Attach the foam to the top of the closed box and then put the two big boxes together. You're almost done.
You will likely have to put some kind of cover over your phone as the birght sun will make it hard to see the display.
Let's make it work
Mount your phone, turn on your favorite camera app, and align the box. Alignment is performed by pointing the box at the sun so that the shadow created by the box is directly under the box. I use a few old bricks and big rocks to keep it in place. Since the eclipse is mid day for those of us on the east coast the box will be nearly vertical. With your phone camera app up you should be able to see the sun's image as a very round circle. If you see any other bits of light you have holes somewhere and need to break out some of the Gorilla tape. Some times you need try blocking off parts of the box with your hand to find the "leaks".
On an iPhone you can trigger the shutter via the volume controls on ear phones. This keeps you from putting preasure on the box and moving it by accident.
Keeping the camera app up for an hour at a time will really chew up your battery. I plan to use an external battery connected to my phone so I don't have to worry about recharging.
I've also purchased a camera app that gives me more control over how the photos are taken plus the ability to set it to take a picture every few seconds. With this I can set the camera to shoot over periods of time while I actually watch the sun.
While not a requirement I have access to 3 phones. I plan to put all 3 of them on the "box" so one can do movies and the other 2 taking time lapse higher quality stills.
So, am I nuts or what?
A few pictures to help out.
Assembled version 1. More prototype than anything else. But it did work. Camera mounts are for an iPhone 6s+ and an iPhone 5s.
Version 2 view of inside the bottom box before plugging light leaks.
Image with version 1. Fuzzy edges caused by both sky haze and using foam board for target. Plus using used aluminum foil with a not very good hole.
Image from version 3. Note edges are much sharper. Better pinhole, clearer sky, and glossy paper for target.
Version 4 lower half. Note tape for light leaks.
Version 4 inside showing flat black paint and glossy 11×17 paper taped to foam board.
Black paint made it hard for camera to focus which mean it was working.
Version 4 with 2 boxes joined together. Note the holes on the top for the pinhole and the camera lens. This is just a friction fit so it's easy to take apart and toss into the back seat of your car.
Version 4 close up of top.
Version 4 with foam board on top. Center cut out is for pinhole lens holder. Larger cutout is for my iPhone.
Later I'll add 2 more cutouts to allow for all the phones we have.
Lens holder showing 2 halves. Clear tape is applied to the surfaces to allow for tape to hold the top on but not tear the foam board when removing the top.
Lens holder with aluminum foil held into place. The pinhole is there but so small as to not be seen.
Everything assembled but the cables. Note the cutout at the bottom of the phone to allow for headphone cable and power.
Comments and corrections welcome.