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Picture of Floppy Disk Sun Filter
Several months ago I posted an Instructable about making a simple sun filter with a black marker and a sheet protector. That approach, although it did block out most of the light, didn't work very well and threw everything out of focus. This one, using a floppy disk and some card stock, works much better and doesn't take anywhere near as long to make. There's also slightly less of a pink color, though part of the blue component of the color seems to be from UV that makes it through the filter. The effect seems to go away when used with a telescope for some reason. Instead, the disk filters the light to a more realistic orange.

Step 1: Supplies

Picture of Supplies
You'll need a camera with optical zoom (this is important, you'll be using the lens barrel to keep the filter attached) a floppy disk, some thick paper, glue, scissors, and tape might be helpful in assembling the mount.
I'm also using an old computer as a surface. You can use any old computer you  might have laying around, or you can just use a normal table.
 
georgeATM3 years ago
Please note that using homemade filters should only be used for photography and not visual observing. Solar observing is the only activity in astronomy that is inherently dangerous. Using any filter that is not specifically designed for this activity can be dangerous because there are wavelengths of light that the human eye can't see but are still harmful to the structures of the eye, specifically ultraviolet and infrared, that may be getting through the filter. Galileo's blindness in old age may have been caused by observing the sun.

End of scary rant.
Kudos on a fine instructable.
tbh-1138 (author)  georgeATM3 years ago
I included a warning on the last step. I have no idea what wavelengths can get through 4 or 5 layers of floppy disk material, other than that it only lets red and orange through. I'm sure plenty of IR passes right through, as I've seen another instructable using a floppy disk as a filter for IR photography. It would be nice if there were a way to make a filter that first blocks everything but the UV, then shift the UV into the visible range. From what I've seen in SOHO and STEREO photos the sun looks awesome in UV.

I don't know if what you want is even possible, but if it is, it would cost a lot more than a floppy disc. There is a thing for DSLR cameras that is called a "black" neutral density filter. I think, I'm not sure and you should not do it without studying a bunch on it, but I think that you can take photos of the sun with it. I plan on getting one eventually because I love taking photos of night, stars, lights at night, basically, anything that I can use a long shutter speed on.

GregC212 months ago

Also note that if using a telescope you should block off your finder scope as well. The sun will fry any crosshairs in a nanosecond if left unprotected. Remember a telescopes job is to collect as much light as it can and concentrate it in your eyepiece. Plastic components wont last long as the heat increases rapidly.