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reply to CylonRed

Re: Cool pics of the sun from a backyard..

here are links to the curves for some typical hoya / nikon etc filter glasses:

using the hoya / nikon names -


(the number is the nM at which transmission/blocking is 50%/50%, e.g R60 is 50% transmission at 600 nM.)

showing almost total transmission of invisible IR infrared in the 1800+ nM range -


note that most glasses inherently block most UV,
but, as rconing notes,
many glasses can pass all of some wavelengths of invisible IR infrared light.

the visual band is roughly 400-700 nM,
UV is below 400,
IR is several octaves above 700.

again, if doing any photos of the sun with long lenses, avoid looking through the viewfinder at the magnified toobright image of the sun, which can instantly burn your eye inside.

in general, compare the size of the diameter of your eye iris, about 1/8" - 1/4", with the diameter of your telephoto lens, about 2"; the lens is collecting bout a hundred times more light, 100 times more bright, than your eye.

even the foil filters can have passbands in IR and be unsafe.

sunspot viewing and sunspot images are interesting cause you can use them to predict solar effects on earth, and you can use the movement of the spots to determine the rotational speed of the sun.