One of the things I've been concerned about is frying the camera while shooting this eclipse. Do you remember using a magnifying glass as a kid and setting dry leaves on fire? Well, this is a rather large lens we'll be using pointed directly at the remnant of the sun visible during the eclipse. Focusing this image on the camera's $1000+ sensor seems like an ill-advised proposition capable of setting the whole rig on fire. Wouldn't that be a hoot.
Years ago I bought a spotting scope to take just this shot but shelved it due to low quality test images. Still, it just occurred to me to use it as a quick approximation of what might happen pointing it at full sun.
So this afternoon I mounted it on a tripod and tried various materials on it for the ultimate flame test. First, a piece of paper with the "sun-spot" sized to how big it will be on the camera sensor when we use the real lens.
No flames. Not even smoke. Interesting. I tried a thin sheet of finely woven packing foam -- not even melty plastic. Hmmmm... so I tried my hand... fingers... kinda pulling away as I thought I felt some heat.
It felt kinda warm? But not painful by any means. And this was a worst case test -- the sun was higher in the sky than it would be during our test, and while the real lens will concentrate 7x as much light in the same area, only 1/14th of the sun will be visible during the eclipse. We'll probably use an 8x filter to darken the image as well as an additional margin of safety, but it looks like we're well below the fire hazard range. And I'm very glad to breathe some sort of relief on one of the risks we were facing for this shoot.
I leave you with a cute shot taken with a cellphone camera through this scope. Almost looks like the camera's sensor was on fire...