Hypatia's Protege
- Joined Mar 1, 2015
- 3,228
If you cannot locate 'reputable' 'eclipse glasses' or a #14 welder's shade you may 'cascade' welder's shades as described by @Aleph(0) (quoted below) -- Hence any combination totaling 15 is equivalent to a #14 shade. Please note that #10s and #5s are available from most 'bricks and mortar' hardware retailers (as are #8s - A pair of #8s (#15 equivalent) will be a little dark but quite acceptable...Did you get a pair of super secret eclipse specs? I understand they are almost impossible to get right now. Not sure if I would even trust them. Better just to watch it on TV.
Welder's glass shade numbers aren't the same as optical density and don't add like most ppl think when cascaded!
So minimum optical density for safe solar observation at sea level=5
So for welder's glass OD=(3/7)*(Shade_number-1)
So minimum shade number for sea level solar observation ≈ #12.666667
So #14 gives good safety margin for higher altitude or in case of slightly out of spec filter.
So u can see from formula that shade numbers cascade like this: SN(cascade)=(SN1+SN2)-1
Why not? It's our dimeSo why is NASA spending all of this money just to study the sun's corona? I thought they have been doing this for more than a century without the aide of a natural eclipse by using a chronograph?
Best regards
HP
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