MadSci Network: Astronomy

Re: Is it safe to look at the sun through a welding mask?

Date: Tue Aug 24 13:40:36 1999
Posted By: Tom Stickel, Grad student, Optometry, Indiana University School of Optometry
Area of science: Astronomy
ID: 933246345.As

Hey there,
  I realize that we've missed the eclipse, so hopefully you didn't use your 
grade 10 welding mask to view it.  The sources I looked at (Sky 
an Telescope, July 1991, p. 80) recommended using at least a grade 12, and 
preferably a grade 14 visor (which lets through 1 out of every 370,000 
photons striking the front surface.  Any way you look at it, viewing an 
eclipse directly is not the safest route to go.  Only one second of direct 
viewing of the sun can result in permanent damage.  This is often heat 
damage caused by infrared radiation, which is why UV blocking sunglasses 
won't keep you safe while viewing an eclipse either.  As I was saying, try 
to stick to projection methods of viewing such as mirrors or pinholes.  
  But if you absolutely insist on viewing an eclipse directly, make sure 
you use a filter that blocks out nearly all visible light as well as 
infrared and UV radiation.  Most eclipse glasses are made from aluminised 
Mylar or a black polymer.  Back in the day, when film contained silver 
nitrate, you could view eclipses through exposed negatives, BUT THIS IS NO 
LONGER TRUE!  Today's plastic films offer no infrared protection! 
  For more info, check out this eclipse viewing site by clicking below.  

Good Luck,


Safe eclipse viewing

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