Eclipse Pin-hole camera

 It's been a while since I posted here. Excuses? I have none.

What I do have is a pinhole camera ready for Monday's eclipse. Hopefully it works better than 2017. then I'd just perforated a bit of foil in a random box. Yea, didn't work so well. This time I did a little homework.

First, the math. Shhh. don't tell my wife I'm doing math, she gets mad when I say that word.

The focal length of a pinhole camera turns out to be 

focalLength = (holeDiameter / 0.03679)^2

I have some sewing pins with a diameter of 0.58mm so my focal length would work out to 248.5mm or for us Mericans 24.85cm*(1"/2.54cm) = 9.783 inches. That works out to a little more than 9 13/16 in. That's great because I have a banker's box that's 10 1/2 in deep. If I glue some white card stock to a piece of 3/4 in foam board I come really close to that. Or close enough that I can adjust by sliding the foam around in the box and pinning it in place when I get a sharp image. 

The viewing angle formula is:

viewAngle = tan^-1 * ((diameter/2) / (thickness / 2)) * 2

For a piece of aluminium foil that's a wide field of view. I really don't want to have all the tree branches and other light pollution rendered inside my banker's box so I need something thicker. Turns out an old CD is 1.23mm thick and produces a viewing angle of 5.4 degrees. That should isolate the eclipse fairly well... I hope. 

Unfortunately it means that I'll need to have the perforated CD almost perfectly tangential to the eclipse if I want to get any images and it's unlikely I'll be able to do a time laps. Hopefully the sky clears today so I can do some test runs this afternoon.

Finally, the imager will be my cell phone camera. I've cut a hole near the hole in the CD so I can place my cell phone over to take pictures of the image rendered in the banker's box. My initial tests in my office worked out fairly well. I was able to get a sharp image of one of the LED pot lights in my office. The image is sharp enough to render individual LED elements in the flood light. This is not something you can see if you look at the light. My only concern here is the glare of seeing what's on the cell phone display in the glare of full daylight. For now my plan is to tape the cell phone case down to the box then put the cell phone in the case when it's show time. That should allow me to set it up and minimize movement when taking pictures.

One last thought. The imageDiameter = tan(viewAngle) * 2 * focalLength or ~1.8 inch
I'll have to see if the actual sun image is that size. My guess is no given my initial tests using the LED flood light in my office which had an image size of about 1/4 inch.

UPDATE 2024-04-08 16:28 EDT

I did get some pictures through the Pinhole Camera by placing my cell phone adjacent to the pinhole. 

Not too shabby though I wish I'd zoomed the camera before taping it to the box and rendering my touch screen nearly useless. I've also got a time laps video but since everyone jumped on 5G to share their pictures and jabber away on social media, I have to wait a bit for that.

This picture, I took directly with my cell phone holding my eclipse glasses over the lens to act as a filter.