2017 total eclipse question (eye protection)

[K Frame]

"technically you can't."

This.

Very few places in the US have the equipment needed to test these lenses to ensure that they are safe.

Counterfeit ones can act like certified lenses but can still allow dangerous amounts of UV radiation to pass through.

[HeroHog]

https://youtu.be/yoMEbDcFK7U

TOP 10 ECLIPSE DAY Things to know (please share) - Smarter Every Day 174

[Brad Johnson]

For limited use like this, I generally used a 10 and a 5 stacked.  Even better if you can find the 5 as glasses (wonderful product for migraine sufferers) and the 10 as a hood that works over them.  14s seem to disappear from Tractor Supply when there's a solar event on the calendar.

For anyone interested, I think this is the calc for stacked welding optics:

Effective Shade Number = S+(S-1)

Brad

p.s. - Someone please confirm before anyone burns out their eyeballs based on my spotty memory...

[MechAg94]

"technically you can't."

This.

Very few places in the US have the equipment needed to test these lenses to ensure that they are safe.

Counterfeit ones can act like certified lenses but can still allow dangerous amounts of UV radiation to pass through.

Would it be better to just go to an industrial supply and get the right type of welding goggles?

[Kingcreek]

I picked up the ones from the local library that they received on a grant from NASA.
I think they are defective. Can't see a damn thing through em.
Many places including the library are having eclipse parties.

[zxcvbob]

Would it be better to just go to an industrial supply and get the right type of welding goggles?

Yes.  I went to the local one a few days ago and they still had lenses -- but obviously no shade 14's.  A guy at work said he went there today and they were picked clean.

I have a 5, 8, 9, and 10 here in my office.  (I'll start with the 5+10, and if that's too dim switch the 10 to a 9)  And an old pair of brazing goggles at home with an unmarked lens (probably a 4 or 5), and I don't know what my arc welding hood has in it right now (probably a 10 or 12)

You might could goto someplace like Harbor Freight and get three shade 5's and stack them.

#5 is very common for brazing or cutting; don't remember which.

[230RN]

https://youtu.be/yoMEbDcFK7U

TOP 10 ECLIPSE DAY Things to know (please share) - Smarter Every Day 174

FWDED.  Now I gotta look up those ground snake shadows (#6).  Never heard of them

TNX,
Terry

[230RN]

...
Now I gotta look up those ground snake shadows (#6).  Never heard of them before.
...
Terry

Shadow bands (shadow snakes) and other facts pretty well covered such as C1-C4, etc. This guy is pretty good; first time I've seen one of his videos:

http://kgab.com/watch-out-for-creepy-shadow-snakes-during-wyomings-eclipse-video/

Shadow Bands: 4:20 ff

From the description, with its rarity and brevity, it reminds me a little of the "Green Flash" phenomenon, which is also rare and brief and only occurs just as the sun is peeping over an unobscured horizon, sunrise or sunset.  I wonder if it's related to the spikes of light from the corona or Bailey's Beads.

Hm.  I guess I'll leave that one to the pro astronomers and diffraction experts.  Strikes me that it's a diffraction effect modified by the shifting of the atmosphere, like in the way a distant jet plane's sound comes and goes.  Except with light waves instead of sound waves.  Somehow.  Or other.

There is an app for precise (and verbal) locations and times available on the app store:  "solar eclipse timer" is its name, see around 12:52 in the cited video.

Parenthetical remarks and ETAs:
(It's interesting to me that the observation of wildlife behavior has only now been discussed --or only this time around that I know of and I never fail to mention it. That was the primary surprise when we went to see the total in Maine back in the '60s.  The forest seemed to go dead silent.  That one was a cloudy one, so very disappointing.  But you plays the cards you gots.)

(I just got word from Son2 that the glasses he gave me were part of the Amazon refund.  Drat.  I guess it's back to pinhole camera time at my 93% viewing area.  Or I've got an old pair of 1.25 driving glasses I could pull the lens out of and stop down to 1/8" or 1/16th" and set up a screen 31.496" away:

39.37" (one Meter) ÷ 1.25 (diopters of glasses) = 31.496" focal length if I'm figgerin' right. Well, call it 31-1/2" anyhow.

With that lens, a 1/8" pinhole would be equivalent to an f-number of 252, 1/16" would be f 504 of course (doubled).

Double-drat.  'Sperimink time today! And I had planned to vacuum the floors.  )

Terry, 230RN

REF (Green Flash):
https://en.wikipedia.org/wiki/Green_flash

[HeroHog]

Know what I'm gonna do during this eclipse? Sit in this here chair. I'm still good from the one I saw back in Mar 7, 1970.

Handy tool here: https://www.timeanddate.com/eclipse/in/usa/shreveport