On 28/07/17 03:21, wrote:
On Thursday, May 17, 2012 at 11:53:14 AM UTC-6, mike wrote:
I want to look at the eclipse this weekend.
Everybody says a #14 welding shade is good.
I don't have one.

So, how do the numbers stack up when you use 2?
I'm guessing it's not linear, so 7+7 doesn't = 14???

What's the math for stacking welding shades?

Thanks, mike
Relevant all over again for August 21, 2017.

So based on A Norton's formula:

4 5 6 7 8 9 10 11

4 7 8 9 10 11 12 13 14
5 8 9 10 11 12 13 14 15
6 9 10 11 12 13 14 15 16
7 10 11 12 13 14 15 16 17
8 11 12 13 14 15 16 17 18
9 12 13 14 15 16 17 18 19
10 13 14 15 16 17 18 19 20
11 14 15 16 17 18 19 20 21

So the first column and row are the shades you are adding. Follow 14 on the diagonal to combine your shades. So a #10 + a #5 is #14.
If you want to check the formula the spread sheet link is:

https://docs.google.com/spreadsheets...it?usp=sharing

My neighbours borrowed a couple of my fixed shade filters when they went
on a cruise in IIRC 2015 for the Norwegian eclipse and they borrowed my
11EW filters and were very happy and many others on the cruise were
envious as the view my neighbours got of the eclipse was apparently far
superior to that through the cruise supplied cheapy filters.

That can be done with many small sized optics even a pin hole in a box
to project to the other side.

DO NOT DO THIS through an 8" or larger scope. The optics might shatter.
Those scopes have front of the main optical plane a cover with a
shielded portal. Gold plated as I recall.

I have both 8 and 11" scopes and protect them at all times.

Martin

On 8/3/2017 5:29 PM, DoN. Nichols wrote:
On 2017-08-03, wrote:
This old thread but applies now with 2017 eclipse...

Someone says the numbers DO add up so I figure using two number 10s
from cheap Harbor Freight welding goggles will be okay. I wouldn't plan
on staring at it for extended periods in any case. Would be cool to put
it on front end of telescope and view, but that's pushing it.

With a telescope, the way to go is (assuming that it is on a
tripod) is to mount a white piece of cardboard (or white paper supported
by cardboard) at a proper distance behind the eyepiece, and adjust the
focus so it projects a sharp image onto the cardboard. The more
distant, the larger the image if the focus range is enough.

If the telescope is smaller than the cardboard, put another
piece of cardboard around the back end of the telescope eyepiece, to
make sure that the target cardboard is in the shadow.

If you have a fairly large diameter, mirror lens telescope
(much shorter than the glass refractor only 'scopes for a given power),
you can use a smaller filter mounted off center in some opaque
cardboard, and mount it off center, so it covers the area between the
center mirror mount and the outer rim of the front lens. This reduces
the amount of energy coming through the 'scope, so the filter can be
weaker and smaller than needed for the full aperture of the 'scope.

Long ago
I used 6 polarized filters (crossing two at 90 degrees, then three sets
at 120 degrees) which made it almost black (easy to see sun) but don't
know if it blocks UV and IR. I was stupid (younger..) and used it to
look at the sun through a telescope... didn't take long and image got
blurry (I don't remember seeing the sun) so looked at filter and it was
MELTING...

*Always* put the filter at the input end of the telescope.

dumb bass... remember burning leaves with sun using mag glass
and a telescope is much more powerful... glad I didn't burn my eyeballs
(am 60 now so damage from 40 years ago would be apparent).

Yes.

Good Luck,
DoN.

"David Billington" wrote in message news
On 28/07/17 03:21, wrote:
On Thursday, May 17, 2012 at 11:53:14 AM UTC-6, mike wrote:
I want to look at the eclipse this weekend.
Everybody says a #14 welding shade is good.
I don't have one.

So, how do the numbers stack up when you use 2?
I'm guessing it's not linear, so 7+7 doesn't = 14???

What's the math for stacking welding shades?

Thanks, mike


5 years ago there was a discussion here on RCM of this very question.
The short answer is S(sum) = S1 + S2 -1.
For full discussion see he
https://groups.google.com/forum/#!to...ng/rjyeFrVlxJM
Art

On Thu, 3 Aug 2017 10:18:58 -0700 (PDT), wrote:

This old thread but applies now with 2017 eclipse...

Someone says the numbers DO add up so I figure using two number 10s
from cheap Harbor Freight welding goggles will be okay.

they do add but not linearly. The sum is usually one less than the
numerical sum.

I have a wide variety of welding filters here in the lab because of
the wide variety of materials I have to induction heat in a demo,
photograph the heating and send the results to a potential client.

I've built a mechanism to hold a stack of filters in front of my
camera and have installed open source software on the camera to
provide an intervalometer function. The combination of filters that
make both my eyes and my camera happy are a #6 and a #12. According
to a chart I have, that's equivalent to a #15 filter.

Your stack of 2 #10s will probably be too dense, as my chart shows
them to be equivalent to a #18. Especially if you're photographing
the event, you want your camera to be stopped down and timed out
almost completely so that it'll have enough range to see the corona
and solar flares during totality.

Even when just watching, a stack of 2 or 3 filters will be almost
essential. During the last eclipse I used a welding hood with a #13
filter. When totality happened, I flipped up the filter and watched
unfiltered. When that first little bit of the sun shown at the end of
totality, my eyes were instantly dazzled. They teared up and I saw
spots for most of the rest of the event. I wish I'd had a #2 or #3
filter to watch totality with.

While we're on the topic, I'll say something about the cheap cardboard
glasses being sold or given away. I got 2 sets. I drove to my
photographing place, laid down in the back of my truck, put the
glasses on, opened my eyes and... Lasted for about a minute. The
filter is dense enough but the surround is so narrow that glare from
my cheeks reflecting off the back side of the filter dazzled me.

So I've made up a couple of shields out of poster board that will
protect my whole face from the glare.

So any of y'all planning on using those cheap cardboard glasses need
to do a dry run with full sunlight to see if you can stand the glare.

John


John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address

On Friday, August 4, 2017 at 10:43:16 AM UTC-4, Neon John wrote:
On Thu, 3 Aug 2017 10:18:58 -0700 (PDT), wrote:

This old thread but applies now with 2017 eclipse...

Someone says the numbers DO add up so I figure using two number 10s
from cheap Harbor Freight welding goggles will be okay.

they do add but not linearly. The sum is usually one less than the
numerical sum.

I have a wide variety of welding filters here in the lab because of
the wide variety of materials I have to induction heat in a demo,
photograph the heating and send the results to a potential client.

I've built a mechanism to hold a stack of filters in front of my
camera and have installed open source software on the camera to
provide an intervalometer function. The combination of filters that
make both my eyes and my camera happy are a #6 and a #12. According
to a chart I have, that's equivalent to a #15 filter.

Your stack of 2 #10s will probably be too dense, as my chart shows
them to be equivalent to a #18. Especially if you're photographing
the event, you want your camera to be stopped down and timed out
almost completely so that it'll have enough range to see the corona
and solar flares during totality.

Even when just watching, a stack of 2 or 3 filters will be almost
essential. During the last eclipse I used a welding hood with a #13
filter. When totality happened, I flipped up the filter and watched
unfiltered. When that first little bit of the sun shown at the end of
totality, my eyes were instantly dazzled. They teared up and I saw
spots for most of the rest of the event. I wish I'd had a #2 or #3
filter to watch totality with.

While we're on the topic, I'll say something about the cheap cardboard
glasses being sold or given away. I got 2 sets. I drove to my
photographing place, laid down in the back of my truck, put the
glasses on, opened my eyes and... Lasted for about a minute. The
filter is dense enough but the surround is so narrow that glare from
my cheeks reflecting off the back side of the filter dazzled me.

So I've made up a couple of shields out of poster board that will
protect my whole face from the glare.

So any of y'all planning on using those cheap cardboard glasses need
to do a dry run with full sunlight to see if you can stand the glare.

John


John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address

Good point, and I think I'll do just that. This would, I suppose, ba a perfect application for that black gunk football & baseball players smear on their cheekbones.

BTW, Sometimes life is good. We have a business trip scheduled almost a year ago that will have us in Sun Valley Idaho for the eclipse. Woo Hoo!

Everyone is wasting you time sir. Welding glass is a great was to view the eclipse. Do not go below Shade 11. I don't know how the absorption rate increases when stacked. You can buy 4 1/2" by 5 1/4" glass from Air Gas for $3.20. I am have Shade 12 mounted to my binoculars. Everyone else who is poking a hole in a box or black out curtains that is fine. But spend a few pennies and at lease get the paper shade glasses at 7-11 to see the real thing. This is near a once in a lifetime event don't just watch the reflection.

On Thu, 10 Aug 2017 14:35:38 -0700 (PDT),
wrote:

Everyone is wasting you time sir. Welding glass is a great was to view the eclipse. Do not go below Shade 11.

NASA says number 14:

"One of the most widely available filters for safe solar viewing is a
number 14 welder's glass, available through welding supply outlets.
More recently, aluminized mylar has become a popular, inexpensive
alternative. Mylar can easily be cut with scissors and adapted to any
kind of box or viewing device. A number of sources for solar filters
are listed below. No filter is safe to use with any optical device
(i.e. - telescope, binoculars, etc.) unless it has been specifically
designed for that purpose."

https://eclipse.gsfc.nasa.gov/SEhelp/safety.html

--
Ed Huntress

On Thu, 10 Aug 2017 14:35:38 -0700 (PDT),
wrote:

Everyone is wasting you time sir. Welding glass is a great was to view the eclipse. Do not go below Shade 11. I don't know how the absorption rate increases when stacked. You can buy 4 1/2" by 5 1/4" glass from Air Gas for $3.20. I am have Shade 12 mounted to my binoculars. Everyone else who is poking a hole in a box or black out curtains that is fine. But spend a few pennies and at lease get the paper shade glasses at 7-11 to see the real thing. This is near a once in a lifetime event don't just watch the reflection.

I wonder how many people you'll blind with that suggestion.
Astronomers and medicos say 14 is the shade, not 11.

-
I am a Transfinancial--A rich person born in a poor person's body.
Please stop the hate by sending me money to resolve my money
identity disorder. --anon

I lived in Cambridge, UK for a while - all the welding suppliers
sell-out of #14's as important solar events came around.
Not tried myself, but #14 is the acknowledged and tested filter.

My thought - 'cos it's glass and thick, you cannot damage it in any
way which compromises its filtration without that being absolutely
obvious by reason of the glass being broken.
Same reason as condom moulds for forming from the natural latex are
made of glass - they are either fully intact or fully broken - nothing
in-between is possible.

On Friday, August 11, 2017 at 2:57:26 AM UTC-4, Richard Smith wrote:

Same reason as condom moulds for forming from the natural latex are
made of glass - they are either fully intact or fully broken - nothing
in-between is possible.

Today, I have learned something new. Thanks, Richard.

On Fri, 11 Aug 2017 09:08:02 -0700 (PDT), rangerssuck
wrote:

On Friday, August 11, 2017 at 2:57:26 AM UTC-4, Richard Smith wrote:

Same reason as condom moulds for forming from the natural latex are
made of glass - they are either fully intact or fully broken - nothing
in-between is possible.

Today, I have learned something new. Thanks, Richard.

Right! I always wondered why there was no market for condom blowout
patches...

--
Ed Huntress

On 8/11/2017 10:28 AM, Ed Huntress wrote:
On Fri, 11 Aug 2017 09:08:02 -0700 (PDT), rangerssuck
wrote:

On Friday, August 11, 2017 at 2:57:26 AM UTC-4, Richard Smith wrote:

Same reason as condom moulds for forming from the natural latex are
made of glass - they are either fully intact or fully broken - nothing
in-between is possible.

Today, I have learned something new. Thanks, Richard.

Right! I always wondered why there was no market for condom blowout
patches...

It's not like you will ever have that problem is it, ya bareback
butthole surfer?

Now now Ed That is wishful thinking.

Martin

On 8/11/2017 11:28 AM, Ed Huntress wrote:
On Fri, 11 Aug 2017 09:08:02 -0700 (PDT), rangerssuck
wrote:

On Friday, August 11, 2017 at 2:57:26 AM UTC-4, Richard Smith wrote:

Same reason as condom moulds for forming from the natural latex are
made of glass - they are either fully intact or fully broken - nothing
in-between is possible.

Today, I have learned something new. Thanks, Richard.

Right! I always wondered why there was no market for condom blowout
patches...

On Sat, 12 Aug 2017 22:58:09 -0500, Martin Eastburn
wrote:

Now now Ed That is wishful thinking.

Martin

I've never minded much being called a cheapskate, but I guess one can
carry it too far...

-
Ed Huntress


On 8/11/2017 11:28 AM, Ed Huntress wrote:
On Fri, 11 Aug 2017 09:08:02 -0700 (PDT), rangerssuck
wrote:

On Friday, August 11, 2017 at 2:57:26 AM UTC-4, Richard Smith wrote:

Same reason as condom moulds for forming from the natural latex are
made of glass - they are either fully intact or fully broken - nothing
in-between is possible.

Today, I have learned something new. Thanks, Richard.

Right! I always wondered why there was no market for condom blowout
patches...

On Thursday, May 17, 2012 at 1:53:14 PM UTC-4, mike wrote:
I want to look at the eclipse this weekend.
Everybody says a #14 welding shade is good.
I don't have one.

So, how do the numbers stack up when you use 2?
I'm guessing it's not linear, so 7+7 doesn't = 14???

What's the math for stacking welding shades?

Thanks, mike

My welder's supply store stocks #5 and #10. I bought one of each and stacked them and they compare favorably to the #14 i already have. Mathwise, they check out also (OD = 5.564)

On Thursday, May 17, 2012 at 1:53:14 PM UTC-4, mike wrote:
I want to look at the eclipse this weekend.
Everybody says a #14 welding shade is good.
I don't have one.

So, how do the numbers stack up when you use 2?
I'm guessing it's not linear, so 7+7 doesn't = 14???

What's the math for stacking welding shades?

Thanks, mike

It is not linear 7+7 =/= 14

Simply put S_1 + S_2 - 1 = S_true

Example if you have two shade 7s:
7+7-1=13 Not Safe

On Thursday, May 17, 2012 at 6:29:31 PM UTC-7, Steve B wrote:
"mike" wrote in message
...
I want to look at the eclipse this weekend.
Everybody says a #14 welding shade is good.
I don't have one.

So, how do the numbers stack up when you use 2?
I'm guessing it's not linear, so 7+7 doesn't = 14???

What's the math for stacking welding shades?


Thanks, mike

Sent my wife today for two 4 x 5 shade 14 lenses. They said they were out,
and had sold 14,000 lenses. We are SMACK DAB in the middle of the path here
in Toquerville, Utah. My NexGen only goes up to 13. What's up with that?

Steve

The NASA site says that between 12 and 14 is safe but that some find 12 to bright and other 14 to dark but you can't really get 13. There are a lot of "internet experts" who just run with 14 and spout it as gospel.

On Thursday, May 17, 2012 at 1:53:14 PM UTC-4, mike wrote:
I want to look at the eclipse this weekend.
Everybody says a #14 welding shade is good.
I don't have one.

So, how do the numbers stack up when you use 2?
I'm guessing it's not linear, so 7+7 doesn't = 14???

What's the math for stacking welding shades?

Thanks, mike

you can not stack the lens, can still have severe damage, this is coming directly from NASA.

On Thu, 17 Aug 2017 12:47:53 -0700 (PDT), wrote:

On Thursday, May 17, 2012 at 1:53:14 PM UTC-4, mike wrote:
I want to look at the eclipse this weekend.
Everybody says a #14 welding shade is good.
I don't have one.

So, how do the numbers stack up when you use 2?
I'm guessing it's not linear, so 7+7 doesn't = 14???

What's the math for stacking welding shades?

Thanks, mike

you can not stack the lens, can still have severe damage, this is coming directly from NASA.

Direct from NASA, who also gave us Global Warming.

So, you're steering people into buying the cardboard and mylar eclipse
viewing glasses from the Dollar Tree, are ya?

I'll take my chances with indirect viewing, thanks. Having used
pinholes in cards before, I know it works and is detailed. Will try
the binoculars this time, directed onto a card underneath, hopefully
with a larger picture than the pinhole.

-
I am a Transfinancial--A rich person born in a poor person's body.
Please stop the hate by sending me money to resolve my money
identity disorder. --anon

On Thursday, August 17, 2017 at 3:47:57 PM UTC-4, wrote:
On Thursday, May 17, 2012 at 1:53:14 PM UTC-4, mike wrote:
I want to look at the eclipse this weekend.
Everybody says a #14 welding shade is good.
I don't have one.

So, how do the numbers stack up when you use 2?
I'm guessing it's not linear, so 7+7 doesn't = 14???

What's the math for stacking welding shades?

Thanks, mike

you can not stack the lens, can still have severe damage, this is coming directly from NASA.

Dear Smm...., what exactly do you mean by "you can not stack the lens"? We're talking about stacking the solar filters, that is, the darkening filters.. And, which bit of info exactly "is coming directly from NASA"? Are you employed by NASA? Or are you referring to a document from NASA--if so, would you link to it?

- Neu

On Thursday, July 27, 2017 at 10:21:07 PM UTC-4, wrote:
On Thursday, May 17, 2012 at 11:53:14 AM UTC-6, mike wrote:
I want to look at the eclipse this weekend.
Everybody says a #14 welding shade is good.
I don't have one.

So, how do the numbers stack up when you use 2?
I'm guessing it's not linear, so 7+7 doesn't = 14???

What's the math for stacking welding shades?

Thanks, mike

Relevant all over again for August 21, 2017.

So based on A Norton's formula:

4 5 6 7 8 9 10 11

4 7 8 9 10 11 12 13 14
5 8 9 10 11 12 13 14 15
6 9 10 11 12 13 14 15 16
7 10 11 12 13 14 15 16 17
8 11 12 13 14 15 16 17 18
9 12 13 14 15 16 17 18 19
10 13 14 15 16 17 18 19 20
11 14 15 16 17 18 19 20 21

So the first column and row are the shades you are adding. Follow 14 on the diagonal to combine your shades. So a #10 + a #5 is #14.
If you want to check the formula the spread sheet link is:

https://docs.google.com/spreadsheets...it?usp=sharing

Let's cite sources, and stop speculating re losing eyesight.

By the way, anorton, was your source for the formula SN = 1 + (7/3) OD (stacking welding lenses) this article? http://www.astronexus.com/node/3 Just curious.

NASA & the NSF's AAS: welding shade 12 protects eyesight from the sun.

Aside from relying on stacking welding filter lenses according to a formula to reach Shade #14, notice that the American Astronomical Society features this article (link below) €œSolar Eclipse Eye Safety€� by Professor B. Ralph Chou, an optometry professor with a degree in astronomy; he's also lead author of the solar viewing standard ISO 12312-2.

On special ISO eclipse glasses vs. welding lens shade 12-14, Chou's article states, "the transmittance requirements specified for welding filters in the standards for occupational eye protection are more stringent than the [solar viewing] ISO 12312-2 standard.€�

Chou on shade 12 vs. 14: €œThe selection of the welding filter shade number is a matter of personal preference in comfort and will depend on atmospheric conditions and personal glare sensitivity. Filters with shade number 12 should be adequate to protect the eyes, but the solar image may be uncomfortably bright. Some observers may find that the solar image viewed through a shade 14 filter is too dim.€�

The one welding shop I asked said they did sell shade 13 replacement lenses for welding helmets, but they'd sold out.

But don't believe me until you've read Prof. Chou's €œSolar Eclipse Eye Safety€� yourself at:
https://eclipse.aas.org/sites/eclips...Eye-Safety.pdf

AAS approves shade 12 to 14 he
https://eclipse.aas.org/eye-safety/iso-certification

NASA approves shade 12 to 14 he
https://eclipse2017.nasa.gov/safety

They both mention that some people will find shade 14 too dim for viewing the eclipse. And shade 12 too bright, but safe for eyesight.

On Fri, 18 Aug 2017 10:11:41 -0700, Larry Jaques
wrote:

On Thu, 17 Aug 2017 12:47:53 -0700 (PDT), wrote:

you can not stack the lens, can still have severe damage, this is coming directly from NASA.

Direct from NASA, who also gave us Global Warming.

That's total BS from NASA.

The sun's color temperature after the light has filtered through the
atmosphere is about 5200 deg. My company makes custom induction
heaters. We got a commission to design and build a platinum
reclaiming furnace. Since a BB of platinum is worth about $4000, I
used boiling copper as the substitute during development. Copper
boils at 4644 deg F - very close to the sun's intensity. I used a
welding hood with stacked #8 filters to comfortably observe and
photograph the furnace. Yet the sun, which is just a few hundred
degrees away will somehow commit voodoo on welding filters? BS.

So, you're steering people into buying the cardboard and mylar eclipse
viewing glasses from the Dollar Tree, are ya?

The ones with both ANSI and UL certification are OK. They're still
uncomfortable to use since the sun's reflection off one's cheeks
reflected off the back side of the glasses causes strong eye strain.

I don't have any of that black makeup that athletes use under their
eyes so strips of black electrical tape will substitute.

Those are for my wife's use. I'll be using my digital welding hood
that goes up to shade #16. Dialed all the way up, the view of the sun
is comfortable and the hood keeps the heat off my face.

So I've read, a welding arc can reach 9000 deg so if the hood with the
proper filters can handle that it can surely handle the sun at half
the brightness.

I'll take my chances with indirect viewing, thanks. Having used
pinholes in cards before, I know it works and is detailed. Will try
the binoculars this time, directed onto a card underneath, hopefully
with a larger picture than the pinhole.

Have you tested that yet on the sun? I wouldn't expect it to work
very well unless you can mount your binocs on a tripod.


I've fabricated a bracket to hold a stack of welding filters in front
of my camera's lens. I've been practicing on the clear sky sun to
determine what combination of filters makes my camera happy.

With full zoom and digital magnification I can see sunspots. I'm
completely satisfied that this setup is safe for my camera and will
yield fairly spectacular shots.

John
John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address

On Thursday, May 17, 2012 at 12:53:14 PM UTC-5, mike wrote:
I want to look at the eclipse this weekend.
Everybody says a #14 welding shade is good.
I don't have one.

So, how do the numbers stack up when you use 2?
I'm guessing it's not linear, so 7+7 doesn't = 14???

What's the math for stacking welding shades?

Thanks, mike

I'm not sure of the shade # but once before during a partial eclipse my brother doubled two shade glasses in a welding helmet and it was perfect. My dad is dead now or I'd ask what his power was in the helmet. He did it for a living so it probably was two #11's.

I think that saying "if you look at the sun for a moment, you will go
blind forever" is bull****. Similar to most anti-Trump bull****, it is
just ignorant dreck and propaganda.

It is meant to scare people in hopes that this scaremongering would
prevent them from doing truly dangerous stuff, such as staring at sun
for long durations of time. Similar to DARE propaganda and such.

Think about this. When you drive in the morning, evening, or
mountains, you often get sun right in front of your eyes. And you
still keep on driving. Surely, you did not go blind from that.

Similarly, there are many cases when you catch a glimpse of the sun,
say, operating a crane, or doing some outdoor work overhead. I was
craning stuff last week and the sun was right over where the hook
was. It was extremely annoying and I tried very hard to look at it as
little as possible. But still, the sun was right there.

I have no doubt that staring at sun for a long time (more than a
second) would damage your eyes. It is uncomforable enough that people
do not do that.

Now, welding shades are made for professional use to look at powerful
electric arcs right in front of the person. They block most light, UV
and such.

To say that a shade 10 is somehow dangerous, defies common sense.

I have shade 10 welding shades (with gold layer on the outside) and I
tried them to look at the bright sun. They seem to work well, although
the sun appeared to be a bit too bright.

i


i

So in other words I have to 10 shade so if I tapersonally them together than that should be safe ??

So I can double up on 2 #11 weld lenses & Im safe?

On Sun, 20 Aug 2017 12:31:04 -0700 (PDT), wrote:

So I can double up on 2 #11 weld lenses & Im safe?

You'll be safe but you probably won't see anything. That would be
equivalent to a shade 21 if they even make them.

For my camera setup, I'm using stacked #12 and #6 filters, equivalent
to a #15. I have the shutter speed set to 1/60 and run aperture
over-ride. As the obscuration progresses, I'm going to remove the #6
filter. As it nears totality, I'll swap the #6 in and #12 out. When
totality is complete, off comes the #6 for a shot or two of totality.
Then I'll reverse the process as the sun becomes un-masked again. All
in an effort to keep the iris from being forced wide open and
therefore underexposing that shot.

I've spent much of the day optimizing the filter vs zoom that gives me
good shake resistance. The Canon's servo controlled moving lens
element for shake reduction does a spectacular job. I got some pix
today where I can clearly make out the texture of the surface of the
sun, see some sun spots and barely see some streamers.

Fingers crossed that tomorrow will be clear.

John
John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address

On Sun, 20 Aug 2017 16:13:22 -0400, Neon John wrote:

On Sun, 20 Aug 2017 12:31:04 -0700 (PDT), wrote:

So I can double up on 2 #11 weld lenses & Im safe?

You'll be safe but you probably won't see anything. That would be
equivalent to a shade 21 if they even make them.

For my camera setup, I'm using stacked #12 and #6 filters, equivalent
to a #15. I have the shutter speed set to 1/60 and run aperture
over-ride. As the obscuration progresses, I'm going to remove the #6
filter. As it nears totality, I'll swap the #6 in and #12 out. When
totality is complete, off comes the #6 for a shot or two of totality.
Then I'll reverse the process as the sun becomes un-masked again. All
in an effort to keep the iris from being forced wide open and
therefore underexposing that shot.

I've spent much of the day optimizing the filter vs zoom that gives me
good shake resistance. The Canon's servo controlled moving lens
element for shake reduction does a spectacular job. I got some pix
today where I can clearly make out the texture of the surface of the
sun, see some sun spots and barely see some streamers.

Fingers crossed that tomorrow will be clear.

I think it was about 10am that the smoke rolled in from a nearby fire
today. Hopefully, the air will remain clear past 9:19am tomorrow.

-
I am a Transfinancial--A rich person born in a poor person's body.
Please stop the hate by sending me money to resolve my money
identity disorder. --anon

Welding glasses shades 13 or higher are completely safe for viewing the sun as they are 99.9% UV-AB protected

On Friday, August 18, 2017 at 8:29:51 PM UTC-5, Neon John wrote:
On Fri, 18 Aug 2017 10:11:41 -0700, Larry Jaques
wrote:

On Thu, 17 Aug 2017 12:47:53 -0700 (PDT), wrote:

you can not stack the lens, can still have severe damage, this is coming directly from NASA.

Direct from NASA, who also gave us Global Warming.

That's total BS from NASA.

Last time I looked platinum was $1,100 per troy ounce. How many ounces to a BB again?

The sun's color temperature after the light has filtered through the
atmosphere is about 5200 deg. My company makes custom induction
heaters. We got a commission to design and build a platinum
reclaiming furnace. Since a BB of platinum is worth about $4000, I
used boiling copper as the substitute during development. Copper
boils at 4644 deg F - very close to the sun's intensity. I used a
welding hood with stacked #8 filters to comfortably observe and
photograph the furnace. Yet the sun, which is just a few hundred
degrees away will somehow commit voodoo on welding filters? BS.

So, you're steering people into buying the cardboard and mylar eclipse
viewing glasses from the Dollar Tree, are ya?

The ones with both ANSI and UL certification are OK. They're still
uncomfortable to use since the sun's reflection off one's cheeks
reflected off the back side of the glasses causes strong eye strain.

I don't have any of that black makeup that athletes use under their
eyes so strips of black electrical tape will substitute.

Those are for my wife's use. I'll be using my digital welding hood
that goes up to shade #16. Dialed all the way up, the view of the sun
is comfortable and the hood keeps the heat off my face.

So I've read, a welding arc can reach 9000 deg so if the hood with the
proper filters can handle that it can surely handle the sun at half
the brightness.

I'll take my chances with indirect viewing, thanks. Having used
pinholes in cards before, I know it works and is detailed. Will try
the binoculars this time, directed onto a card underneath, hopefully
with a larger picture than the pinhole.

Have you tested that yet on the sun? I wouldn't expect it to work
very well unless you can mount your binocs on a tripod.


I've fabricated a bracket to hold a stack of welding filters in front
of my camera's lens. I've been practicing on the clear sky sun to
determine what combination of filters makes my camera happy.

With full zoom and digital magnification I can see sunspots. I'm
completely satisfied that this setup is safe for my camera and will
yield fairly spectacular shots.

John
John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address

On Thursday, August 17, 2017 at 11:05:18 AM UTC-7, wrote:
On Thursday, May 17, 2012 at 1:53:14 PM UTC-4, mike wrote:
I want to look at the eclipse this weekend.
Everybody says a #14 welding shade is good.
I don't have one.

So, how do the numbers stack up when you use 2?
I'm guessing it's not linear, so 7+7 doesn't = 14???

What's the math for stacking welding shades?

Thanks, mike

It is not linear 7+7 =/= 14

Simply put S_1 + S_2 - 1 = S_true

Example if you have two shade 7s:
7+7-1=13 Not Safe

On Thursday, August 17, 2017 at 11:05:18 AM UTC-7, wrote:
On Thursday, May 17, 2012 at 1:53:14 PM UTC-4, mike wrote:
I want to look at the eclipse this weekend.
Everybody says a #14 welding shade is good.
I don't have one.

So, how do the numbers stack up when you use 2?
I'm guessing it's not linear, so 7+7 doesn't = 14???

What's the math for stacking welding shades?

Thanks, mike

It is not linear 7+7 =/= 14

Simply put S_1 + S_2 - 1 = S_true

Example if you have two shade 7s:
7+7-1=13 Not Safe

So two #10 lenses together should be fine, correct?

On Thursday, May 17, 2012 at 12:53:14 PM UTC-5, mike wrote:
I want to look at the eclipse this weekend.
Everybody says a #14 welding shade is good.
I don't have one.

So, how do the numbers stack up when you use 2?
I'm guessing it's not linear, so 7+7 doesn't = 14???

What's the math for stacking welding shades?

Thanks, mike

I just used 2 number 7 welding shades and everything worked fine. I was also able to take pictures with my S6 Edge. I probably wouldn't use anything less than 2 7's which equates to a number 13 shade.

On Thursday, May 17, 2012 at 10:53:14 AM UTC-7, mike wrote:
I want to look at the eclipse this weekend.
Everybody says a #14 welding shade is good.
I don't have one.

So, how do the numbers stack up when you use 2?
I'm guessing it's not linear, so 7+7 doesn't = 14???

What's the math for stacking welding shades?

Thanks, mike

I'm reading this and I still don't understand how the Shade numbers were created and calculated. In some posts I see users indicating camera filters such as #13 for used as a neutral density filter to photograph the sun. In this case I can see that a #13 filter is cutting the exposure by 13 stops. Is this, in essence, what the shade filters mean? In other words does a shade 13 filter cut the amount of light passing through from 100% down to .0122% ?
Taking 100% as a starting point and cutting it by 1/2 you obviously get 50%.. Given this example when you cut 100% 13 time in a roll you get 0122%
If this is the case then an opacity of 4.00 (as measured on a densitomter) would be enough to block the sun's rays when viewing it.

On Mon, 21 Aug 2017 15:23:48 -0700 (PDT), wrote:

On Thursday, May 17, 2012 at 10:53:14 AM UTC-7, mike wrote:
I want to look at the eclipse this weekend.
Everybody says a #14 welding shade is good.
I don't have one.

So, how do the numbers stack up when you use 2?
I'm guessing it's not linear, so 7+7 doesn't = 14???

What's the math for stacking welding shades?

Thanks, mike

I'm reading this and I still don't understand how the Shade numbers were created and calculated. In some posts I see users indicating camera filters such as #13 for used as a neutral density filter to photograph the sun. In this case I can see that a #13 filter is cutting the exposure by 13 stops. Is this, in essence, what the shade filters mean? In other words does a shade 13 filter cut the amount of light passing through from 100% down to .0122% ?
Taking 100% as a starting point and cutting it by 1/2 you obviously get 50%. Given this example when you cut 100% 13 time in a roll you get 0122%
If this is the case then an opacity of 4.00 (as measured on a densitomter) would be enough to block the sun's rays when viewing it.


There are MANY...many standards...all of which have #13 in them.
Bolts, welding, photography, stamp collecting and so forth.


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On Mon, 21 Aug 2017 15:23:48 -0700, timhguitar wrote:

On Thursday, May 17, 2012 at 10:53:14 AM UTC-7, mike wrote:
I want to look at the eclipse this weekend. Everybody says a #14
welding shade is good.
I don't have one.

So, how do the numbers stack up when you use 2?
I'm guessing it's not linear, so 7+7 doesn't = 14???

What's the math for stacking welding shades?

I took the numbers from the web and of course like all the other 'gauge'
numbers (wire, sieve, drill, etc), it's a little bit of a dog's
breakfast: you can see the original logic in the trend, but the actual
numbers are all over the place (*). I don't have the data handy right
now, but I remember that a reasonable approximation was

attenuation = (2.6)^(N-1)

where N is the lens' number. To wit, shade #1 is just transparent glass,
shade #2 attenuates 2.6 times, shade #5 is several hundred times down,
and the strongest shade #14 attenuates about quarter million times. The
formula above is accurate to ~10% for most shades, except few where it's
off by a factor of 2 because imperial. This, however, is good enough,
given that eye sensitivity is logarithmic.


(*) check out the plot of drill diameter vs. drill index number: I would
like to know how THAT came about, as the line is all over the place.

On Mon, 21 Aug 2017 09:19:24 -0700, maddy132335 wrote:

Welding glasses shades 13 or higher are completely safe for viewing the
sun as they are 99.9% UV-AB protected

Shade #13 has an attenuation of around 100000, so stops 99.999% of all
visible light. The attenuation of UV and IR must be much higher, because
your eye can't even protect itself against the invisible radiation.

On Sun, 20 Aug 2017 18:39:19 -0700, Larry Jaques
wrote:


Fingers crossed that tomorrow will be clear.

I think it was about 10am that the smoke rolled in from a nearby fire
today. Hopefully, the air will remain clear past 9:19am tomorrow.

We had a few scattered clouds which enhanced the photos. I got some
spectacular shots with my little setup. I'll be posting them at
johndearmond.com toward the end of the week.

John

John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address

On 2017-08-22, Przemek Klosowski wrote:

[ ... ]

(*) check out the plot of drill diameter vs. drill index number: I would
like to know how THAT came about, as the line is all over the place.

Well ... start with counting the passes of drawing wire through
reduction dies. (They *are* "wire sized drills" after all.

Then, start moving some sizes a bit to avoid near fractional
sizes. (I think that the only counter-example is #7 = 1/4"). This helps
make a number of sizes between the two series. The next thing is when
metric sizes came into the game so move things a little more to make the
combination of wire sizes, fractional sizes, and metric sizes fill in
most of the gaps in the individual sets. Note that when using roll taps
in imperial sizes, the recommended tap drill is often a metric size.

Enjoy,
DoN.

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"DoN. Nichols" wrote in message
...
On 2017-08-22, Przemek Klosowski wrote:

[ ... ]

(*) check out the plot of drill diameter vs. drill index number: I
would
like to know how THAT came about, as the line is all over the
place.

Well ... start with counting the passes of drawing wire through
reduction dies. (They *are* "wire sized drills" after all.

Then, start moving some sizes a bit to avoid near fractional
sizes. (I think that the only counter-example is #7 = 1/4"). This
helps
make a number of sizes between the two series. The next thing is
when
metric sizes came into the game so move things a little more to make
the
combination of wire sizes, fractional sizes, and metric sizes fill
in
most of the gaps in the individual sets. Note that when using roll
taps
in imperial sizes, the recommended tap drill is often a metric size.

Enjoy,
DoN.

http://www.harveytool.com/secure/Con...rill_Chart.pdf
-jsw