2 ms·

I may be "old school" but the "traditional" way is to use a welding mask glass, something you can usually buy "around the corner" for a very little amount of mo

by jaclaz 9y ago

I may be "old school" but the "traditional" way is to use a welding mask glass, something you can usually buy "around the corner" for a very little amount of money and I see that NASA also advises about it: https://eclipse.gsfc.nasa.gov/SEhelp/safety.html https://eclipse.gsfc.nasa.gov/SEhelp/safety.html >One of the most widely available filters for safe solar viewing is a number 14 welder's glass, available through welding supply outlets. And both colour fim and non-silver B&W film are listed by them among the unsafe: >Unsafe filters include color film, some non-silver black and white film, medical x-ray films with images on them, smoked glass, photographic neutral density filters and polarizing filters.

schoen 9y ago
Another longer article on that same site (by a different author) actually mentions the grandparent's suggested method of looking through a floppy disk medium: https://eclipse.gsfc.nasa.gov/SEhelp/safety2.html https://eclipse.gsfc.nasa.gov/SEhelp/safety2.html > Many experienced solar observers use one or two layers of black-and-white film that has been fully exposed to light and developed to maximum density. The metallic silver contained in the film emulsion is the protective filter. Some of the newer black and white films use dyes instead of silver and these are unsafe. Black-and-white negatives with images on it (e.g., medical x-rays) are also not suitable. More recently, solar observers have used floppy disks and compact disks (both CDs and CD-ROMs) as protective filters by covering the central openings and looking through the disk media. However, the optical quality of the solar image formed by a floppy disk or CD is relatively poor compared to mylar or welder's glass. Some CDs are made with very thin aluminum coatings which are not safe - if you can see through the CD in normal room lighting, don't use it!! No filter should be used with an optical device (e.g. binoculars, telescope, camera) unless it has been specifically designed for that purpose and is mounted at the front end (i.e., end towards the Sun). Some sources of solar filters are listed in the following section. > Unsafe filters include all color film, black-and-white film that contains no silver, photographic negatives with images on them (x-rays and snapshots), smoked glass, sunglasses (single or multiple pairs), photographic neutral density filters and polarizing filters. This second NASA author seems to believe that floppy disk media (with the hole covered) may actually be safe for eclipse viewing, just not very effective.

by jaclaz 9y ago

schoen 9y ago

Another longer article on that same site (by a different author) actually mentions the grandparent's suggested method of looking through a floppy disk medium: https://eclipse.gsfc.nasa.gov/SEhelp/safety2.html https://eclipse.gsfc.nasa.gov/SEhelp/safety2.html > Many experienced solar observers use one or two layers of black-and-white film that has been fully exposed to light and developed to maximum density. The metallic silver contained in the film emulsion is the protective filter. Some of the newer black and white films use dyes instead of silver and these are unsafe. Black-and-white negatives with images on it (e.g., medical x-rays) are also not suitable. More recently, solar observers have used floppy disks and compact disks (both CDs and CD-ROMs) as protective filters by covering the central openings and looking through the disk media. However, the optical quality of the solar image formed by a floppy disk or CD is relatively poor compared to mylar or welder's glass. Some CDs are made with very thin aluminum coatings which are not safe - if you can see through the CD in normal room lighting, don't use it!! No filter should be used with an optical device (e.g. binoculars, telescope, camera) unless it has been specifically designed for that purpose and is mounted at the front end (i.e., end towards the Sun). Some sources of solar filters are listed in the following section. > Unsafe filters include all color film, black-and-white film that contains no silver, photographic negatives with images on them (x-rays and snapshots), smoked glass, sunglasses (single or multiple pairs), photographic neutral density filters and polarizing filters. This second NASA author seems to believe that floppy disk media (with the hole covered) may actually be safe for eclipse viewing, just not very effective.