Optical DIY material for photographing Sun

[leroyjenkens]

I procrastinated big time about getting some solar filter or solar film or something to make my camera capable of filming the Sun, and now I can't find anything.
I tried buying replacement glass for welding masks, but even with 4 sheets of it stacked together, the Sun blasts right through it. That stuff doesn't work well at all. It's only slightly foggy. No way you'd be able to weld with only that in front of your face.
I was able to make my own DIY Sun glasses, which is just 6 sunglasses stacked on top of each other. I found that that is the perfect amount for me to be able to look directly at the Sun.
But other than buying 6 more Sunglasses for my camera, which would be difficult to set up, and expensive, does anyone have an idea for some kind of makeshift material I could use? Thanks.

 

[Dr Transport]

i wonder if a silver mylar baloon (unprinted) would work...

this website, https://www.scientificsonline.com/product/mylar-reflective-film-sheets, claims that 90% of visible light is reflected off of it, so that immensely reduces the incident radiation...

 

[leroyjenkens]

That's a good suggestion, but I think any light that isn't reflected off of that material is absorbed by it. It's hard to believe any visible light is penetrating it. The range of wavelengths that it reflects goes from the visible spectrum all through the infrared spectrum. I think if any light is getting through it, it would be in the infrared.
Thank you for the response.

 

[Tom.G]

A lens for arc welding with a density of 12 to 14 works well, and they cost only a few dollars at the local welding supply store or large hardware chain. They are glass with unpolished edges so you may want to add a couple layers of tape around the edges. They are also adequate for visual observation with an optical density that let's thru only 1/(160 000) for the #12 and 1/(1 200 000) for the #14. I use a #13 at 1/(440 000). Much safer than stacking up sunglasses with unknown characteristics!

https://eclipse2017.nasa.gov/safety
About half way down the page under "Additional Safety Information":

"Viewing with Protection -- Experts suggests that one widely available filter for safe solar viewing is welders glass of sufficiently high number. The only ones that are safe for direct viewing of the Sun with your eyes are those of Shade 12 or higher."

 

[CWatters]

Too late for the eclipse now but I used a pinhole projector to observe the transit of Venus some years ago. Not brilliant but dead easy to make at short notice.

 

[Henryk]

Last year, we did go to see the solar eclipse. Unfortunately, the eclipse glasses that we ordered did not arrive.
As a backup, I did two things:
1. Got a pair of welding goggles and an extra filter of the highest density they had in the store. With the two combined and setting the minimum aperture and exposure time of 1/4000 s, I could get the intensity of the light in the linear range of the camera. Still, multiple reflections between the two filters did show up in the pictures. The resultant picture had a strong greenish tint.
2. Bought two neutral density filters. After a test found out that they did not provide enough attenuation of the solar light, so, I put aluminized mylar film in between the two filters. This way I had something I could quickly install in my camera. Two layers got the total intensity into the correct range. The images had a bit of blue tint because metallic absorption depends on the wavelength. Because of two layers, there were still multiple reflections in the images. This is actually way cheaper, it costs a few bucks for a couple of square yards of the film.

 

[James Chase Geary]

The material inside old school 3.5" floppy discs works great as a red/near-IR filter. For sun viewing you'd probably have to stack a bunch of them up, but I'm sure you could make it work.