Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Default How do welding shade numbers add up? Eclipse viewing.

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
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Default How do welding shade numbers add up? Eclipse viewing.

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



A much better idea is to punch a pinhole in the center of one end of a
shoebox , and tape a piece of white paper inside the other end . Point the
pinhole end at the sun , there will be an inverted IIRC image of the sun
on the paper if you've lined it up properly . Similar in principle to a
pinhole camers , you might google "pinhole eclipse viewer" or similar for
more info .
Welding lenses are not really suitable for viewing the sun , though many
people do it ...;
--
Snag
Learning keeps
you young !


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Default How do welding shade numbers add up? Eclipse viewing.

"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?


More than the dark factor, for eclipses, is the UV factor, and window glass
(and plastic) is fairly opaque to UV.
Beer's law would proly indicate that more lenses would be better for UV than
one dark lens, regardless of the net tinting.
http://en.wikipedia.org/wiki/Beer%E2%80%93Lambert_law After all the
bull****, Absorption is linear with thickness.... LOL

Of course, Snag's advice is always good.
--
EA



Thanks, mike



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Default How do welding shade numbers add up? Eclipse viewing.

On Thu, 17 May 2012 15:22:39 -0500, Snag wrote:

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



A much better idea is to punch a pinhole in the center of one end of a
shoebox , and tape a piece of white paper inside the other end . Point
the pinhole end at the sun , there will be an inverted IIRC image of
the sun on the paper if you've lined it up properly . Similar in
principle to a pinhole camers , you might google "pinhole eclipse
viewer" or similar for more info .
Welding lenses are not really suitable for viewing the sun , though
many
people do it ...;


If you have a room available that's sunny at the time of day of the
eclipse, cover up the windows and make a pinhole in the shade. You get a
lot bigger solar disk to view, and if you want you can make multiple
holes.

Because you need to make a tradeoff between brightness and focus, you
want a bigger "pinhole": if I recall correctly a 1/16" or even 1/8" is
appropriate for a ten foot distance.

I remember one solar eclipse where, after leaving the building where us
engineering staff had converted a conference room into a solar
observatory, I noticed that the little sun-dapples filtering through the
leaves of the trees were all little solar eclipse pictures.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

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http://www.wescottdesign.com
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Default How do welding shade numbers add up? Eclipse viewing.


"Existential Angst" wrote in message
...
"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?


More than the dark factor, for eclipses, is the UV factor, and window glass (and
plastic) is fairly opaque to UV.
Beer's law would proly indicate that more lenses would be better for UV than one
dark lens, regardless of the net tinting.
http://en.wikipedia.org/wiki/Beer%E2%80%93Lambert_law After all the bull****,
Absorption is linear with thickness.... LOL

Of course, Snag's advice is always good.
--
EA


Arc welding puts out lot's of UV. Why wouldn't a helmet already
have UV filters in it?
Art




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Default How do welding shade numbers add up? Eclipse viewing.

"Artemus" wrote in message
...

"Existential Angst" wrote in message
...
"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?


More than the dark factor, for eclipses, is the UV factor, and window
glass (and plastic) is fairly opaque to UV.
Beer's law would proly indicate that more lenses would be better for UV
than one dark lens, regardless of the net tinting.
http://en.wikipedia.org/wiki/Beer%E2%80%93Lambert_law After all the
bull****, Absorption is linear with thickness.... LOL

Of course, Snag's advice is always good.
--
EA


Arc welding puts out lot's of UV. Why wouldn't a helmet already
have UV filters in it?


Even better for eclipses!
--
EA


Art



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Default How do welding shade numbers add up? Eclipse viewing.

On 2012-05-17, Artemus wrote:

"Existential Angst" wrote in message
...
"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.


[ ... ]

Arc welding puts out lot's of UV. Why wouldn't a helmet already
have UV filters in it?


It does -- and the auto-darkening ones block the UV even when
they aren't dark.

But -- I suspect that the problem with viewing the sun is more a
matter of IR than UV -- something which can boil the back of your
eyeball. Gas welding glasses have good IR blocking. Arc welding hoods
have good UV blocking. Probably you want both at the same time for
viewing an eclipse -- if you don't go with the pinhole camera approach,
which strikes me as the best -- especially since you can have more than
one person viewing the image at once, instead of fighting over the
filters. :-)

Enjoy,
DoN.

--
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Default How do welding shade numbers add up? Eclipse viewing.

mike used his keyboard to write :
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


Try These for a better view.

http://www.sunguntelescope.com/MAIN.html

http://cdn.transitofvenus.org/docs/B...Sun_Funnel.pdf

--
John G


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Default How do welding shade numbers add up? Eclipse viewing.


"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


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Default How do welding shade numbers add up? Eclipse viewing.

Tim Wescott wrote in
:

I remember one solar eclipse where, after leaving the building where us
engineering staff had converted a conference room into a solar
observatory, I noticed that the little sun-dapples filtering through the
leaves of the trees were all little solar eclipse pictures.


I've seen that before. Way cool, isn't it?



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Default How do welding shade numbers add up? Eclipse viewing.

"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



Several years ago (20? 25?) we had something like a 3/4 eclipse. I was
busy working and didn't have much time to play that day, but I sure found it
interesting seeing all the crescent shapes in the shadows when I walked
under a mulberry tree in my back yard. I'ld never heard of such a thing
before. Oh, I knew about pinhole boxes, and my dad had a reflector for
looking at the sun with his telescope, but I never expected to see such a
blatant display of it so casually like that. I wished I had a camera handy
at the time, but I had work to do, and could only enjoy the site for a few
moments.





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Default How do welding shade numbers add up? Eclipse viewing.


"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


If you convert the shade number (S) into something called "optical density'
(OD), then the OD numbers do add up when you combine them. the formula is:

OD = 0.428 * (S -1)

To convert back from OD to shade # the formula is:

S = 2.33*OD +1

So a shade number of 7 has an OD of 2.568 . Two of these used together have
an OD of 5.136 which is a shade number of 12.96 An OD of 5 or more is
usually considered safe enough for sun viewing.

I have no idea why the welders shade scale was made different than optical
density.

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Default How do welding shade numbers add up? Eclipse viewing.

On Thu, 17 May 2012 18:29:31 -0700, "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


Wear sungalsses under the nexgen?

Remove 333 to reply.
Randy
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"anorton" wrote in message
m...

If you convert the shade number (S) into something called "optical density' (OD),
then the OD numbers do add up when you combine them. the formula is:

OD = 0.428 * (S -1)

To convert back from OD to shade # the formula is:

S = 2.33*OD +1

So a shade number of 7 has an OD of 2.568 . Two of these used together have an OD
of 5.136 which is a shade number of 12.96 An OD of 5 or more is usually
considered safe enough for sun viewing.

I have no idea why the welders shade scale was made different than optical density.


Assuming your equations for Shade # vs OD are correct. Then, since
the equations are linear, you can add Shade #'s too by using
S(sum) = S1 + S2 -1.
Art


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"Artemus" wrote in message
...

"anorton" wrote in message
m...

If you convert the shade number (S) into something called "optical
density' (OD), then the OD numbers do add up when you combine them. the
formula is:

OD = 0.428 * (S -1)

To convert back from OD to shade # the formula is:

S = 2.33*OD +1

So a shade number of 7 has an OD of 2.568 . Two of these used together
have an OD of 5.136 which is a shade number of 12.96 An OD of 5 or more
is usually considered safe enough for sun viewing.

I have no idea why the welders shade scale was made different than
optical density.


Assuming your equations for Shade # vs OD are correct. Then, since
the equations are linear, you can add Shade #'s too by using
S(sum) = S1 + S2 -1.
Art


You are correct. So I guess that 12.96 number above should really be 13 if
not for rounding errors. By the way, the constants in those equations are
more accurately 3/7 and 7/3.



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"anorton" wrote in message
m...

"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


If you convert the shade number (S) into something called "optical
density' (OD), then the OD numbers do add up when you combine them. the
formula is:

OD = 0.428 * (S -1)

To convert back from OD to shade # the formula is:

S = 2.33*OD +1

So a shade number of 7 has an OD of 2.568 . Two of these used together
have an OD of 5.136 which is a shade number of 12.96 An OD of 5 or more
is usually considered safe enough for sun viewing.

I have no idea why the welders shade scale was made different than optical
density.



My SIL called, and was in a tizzy because he could not find one shade 14
lens in all of Las Vegas. So, I went to a local eye doctor, and they had a
case of little cardboard glasses for $2 per. My wife musta got the last of
the 14's at the welding shop, as I called there today, and they have a list
of 38 sold if their special shipment comes in before Sunday evening. I am
pretty much at ground zero, about 15 miles south of Kanarraville, the
epicenter of it.

I am going out tomorrow with my 14 lens on my camera, and try out the
settings I googled up, and make a box to shade me somewhat from the sun,
even though I won't be looking at it, I'll be facing it full on for a good
bit. Gonna have a tripod setup.

Gonna be interesting, both the actual event, and the photography. In
Kanarraville, population 456, they estimate 40,000 people will come in for
this event. There is a lot of farm land around there, so guess there will
be room for all. Some of the farmers will probably clean up on renting RV
spots and such. There's a public baseball park, but it won't hold all the
vehicles, rvs, news satellite trucks, etc. They have 50 portapotties. It's
going to be a zoo, and I'm not going near it. I'll watch it from my back
yard.

Steve, xxtreme SW Utah.


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Default How do welding shade numbers add up? Eclipse viewing.

On 2012-05-19, Edward A. Falk wrote:
On related note, I've discovered that my auto-darkening welding
helmet is not triggered by direct sunlight. How can that be?


They are designed for that, it is a feature, not a bug. The idea is to
NOT be triggered by sunlight, but to be triggered by welding
arcs. This is done for weldors who have to work outside.

Just get a old non-electronic helmet to look at the sun.

i
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Default How do welding shade numbers add up? Eclipse viewing.


"Ignoramus28088" wrote in
message ...
On 2012-05-19, Edward A. Falk wrote:
On related note, I've discovered that my auto-darkening welding
helmet is not triggered by direct sunlight. How can that be?


They are designed for that, it is a feature, not a bug. The idea is
to
NOT be triggered by sunlight, but to be triggered by welding
arcs. This is done for weldors who have to work outside.

Just get a old non-electronic helmet to look at the sun.

i


The sensor appears to have a high pass filter so the sun and
AC-powered lights don't trigger it. My Jackson EQ darkens in sunlight
if I wave my hand across it, a quick test to tell if it's turned on.

jsw


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Default How do welding shade numbers add up? Eclipse viewing.

On 5/17/2012 10:53 AM, 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

Turns out that the weather didn't cooperate.
I found the whole thing very boring. Never found any
images online that showed anything more than a smooth
crescent.
I was expecting some corona or something interesting.


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Default How do welding shade numbers add up? Eclipse viewing.

I shot the eclipse with my Sony A700, and a Perkin-Elmer 800mm
catadiptric lens. Only thing I had that would cover that were my gold
coated full face lenses. I did some test shots in my driveway mid-day to
try and get a handle on shutter speeds and such (since the lens is a
fixed f/11), and noticed that after only a few minutes of experimenting
trying to get an idea where I needed to be for the actual event, my
right eye was starting to get that scratchy eyeball feeling most welders
have experienced.

I ended up shooting through a #13, ISO 160, at 1/4000 sec.
Here's 6 of the best:
http://www.flickr.com/photos/10986502@N08/sets/72157629865291990/

Obviously late WRT to the eclipse, but for someone wanting to view or
photograph the Venus transit, this might give a clue what you're going
to need to dim the sun enough to see Venus against a full sun. I don't
think a welding lens is going to cut it for the Venus transit. Search
ebay for 'solar filter', there's special films available pretty cheaply
that blocks 99.9999% of visible light.

BTW, a neat tool for photographers, is The Photographer's Ephemeris, a
freebie that integrates with Google Earth data. You can specify a date
and pick a location, it'll show where the sun and moon will rise and
set. You can also use it to determine of there's anything in your line
of sight that will interfere with the shot you wish to compose. (well,
big things like hills...) I used it to make sure I picked a location
where I could get a clear shot at the eclipse. Wouldn't have been able
to shoot it from my driveway due to trees.


Jon
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Default How do welding shade numbers add up? Eclipse viewing.

On Wed, 23 May 2012 11:08:02 -0800
Jon Anderson wrote:

snip
I ended up shooting through a #13, ISO 160, at 1/4000 sec.
Here's 6 of the best:
http://www.flickr.com/photos/10986502@N08/sets/72157629865291990/


Nice shots. I used to fool with stuff like this back when I had some
ambition. Film, 35mm stuff that is. I have a couple mediocre digital
cameras but nothing that can use my old 35mm lenses, nor have much
control of the cameras mechanics.

Obviously late WRT to the eclipse, but for someone wanting to view or
photograph the Venus transit, this might give a clue what you're going
to need to dim the sun enough to see Venus against a full sun. I don't
think a welding lens is going to cut it for the Venus transit. Search
ebay for 'solar filter', there's special films available pretty cheaply
that blocks 99.9999% of visible light.


If I really wanted to see this I would get a filter that goes over the
far end of my old Mead 90mm Maksutov-Cassegrain telescope. Like these:

http://www.telescope.com/catalog/sea...d=sun+filte r

When I was a kid I had an old Tasco refractor telescope (Dad bought it
used for me, a big surprise) that happened to have a Sun filter that
screwed on to the eye pieces. It wasn't much, but if you kept the
magnification within reason and used the Sun filter, you could actually
see sunspots pretty good. I even got to watch a partial eclipse with
it


--
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"Jon Anderson" wrote in message
...
I shot the eclipse with my Sony A700, and a Perkin-Elmer 800mm catadiptric
lens. Only thing I had that would cover that were my gold coated full face
lenses. I did some test shots in my driveway mid-day to try and get a
handle on shutter speeds and such (since the lens is a fixed f/11), and
noticed that after only a few minutes of experimenting trying to get an
idea where I needed to be for the actual event, my right eye was starting
to get that scratchy eyeball feeling most welders have experienced.

I ended up shooting through a #13, ISO 160, at 1/4000 sec.
Here's 6 of the best:
http://www.flickr.com/photos/10986502@N08/sets/72157629865291990/

Obviously late WRT to the eclipse, but for someone wanting to view or
photograph the Venus transit, this might give a clue what you're going to
need to dim the sun enough to see Venus against a full sun. I don't think
a welding lens is going to cut it for the Venus transit. Search ebay for
'solar filter', there's special films available pretty cheaply that blocks
99.9999% of visible light.

BTW, a neat tool for photographers, is The Photographer's Ephemeris, a
freebie that integrates with Google Earth data. You can specify a date and
pick a location, it'll show where the sun and moon will rise and set. You
can also use it to determine of there's anything in your line of sight
that will interfere with the shot you wish to compose. (well, big things
like hills...) I used it to make sure I picked a location where I could
get a clear shot at the eclipse. Wouldn't have been able to shoot it from
my driveway due to trees.


Jon


I think you have definitely shown your welding filter is not flat enough for
full aperture photographic or telescopic use.

This site sells a variety of filter types including just the aluminized
mylar and black plastic sheets.
http://thousandoaksoptical.com/solar.html

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On 2012-05-23, Jon Anderson wrote:
I shot the eclipse with my Sony A700, and a Perkin-Elmer 800mm
catadiptric lens. Only thing I had that would cover that were my gold
coated full face lenses. I did some test shots in my driveway mid-day to
try and get a handle on shutter speeds and such (since the lens is a
fixed f/11), and noticed that after only a few minutes of experimenting
trying to get an idea where I needed to be for the actual event, my
right eye was starting to get that scratchy eyeball feeling most welders
have experienced.


Did you do what is recommended for mirror lenses -- make a cover
for the front, with a small (say 1" diameter) hole off center so your
actual aperture is significantly smaller that f/11. That might have
gotten you down to f/32 or so. One reason for this is to minimize the
heating of the central mirror which can otherwise be damaged by the heat
from all that sunlight. (And it also lets you use a less dense filter
-- you might have been able to get away with a #10 or so.

I ended up shooting through a #13, ISO 160, at 1/4000 sec.
Here's 6 of the best:
http://www.flickr.com/photos/10986502@N08/sets/72157629865291990/


BTW -- any idea where the multiple rings on the thin side of the
image came from?

Obviously late WRT to the eclipse, but for someone wanting to view or
photograph the Venus transit, this might give a clue what you're going
to need to dim the sun enough to see Venus against a full sun. I don't
think a welding lens is going to cut it for the Venus transit. Search
ebay for 'solar filter', there's special films available pretty cheaply
that blocks 99.9999% of visible light.


And -- use that off center aperture to cut it down even more and
protect the internal parts of the cat lens.

Enjoy,
DoN.

--
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Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
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On 5/23/2012 12:47 PM, anorton wrote:

I think you have definitely shown your welding filter is not flat enough
for full aperture photographic or telescopic use.


Me and a few others on the Sony/Minolta forum I frequent. Welding
filters are nowhere near optically clear enough for fine photography!
But it was really a last minute decision I made to just go see what I
could do with this lens. I bought it at a yard sale last year and it's
just sat. Got some real magnification, and in one or two, one can barely
resolve mountains on the left side of the moon.

I tried a shot at home the next day, same exact setup sans the filter.
I'm shooting on a high end Berlebach tripod, hanging a big weight off
the column, mirror lockup, remote trigger. Shot the top of a pine tree
that on Google Earth, looks to be about 1/4 mine away. I can count the
individual pine needles, but even with Photoshop sharpening, it's a bit
fuzzy. Since buying that 800mm, I've found I really like macro and wide
angle stuff, so decided last night to see if I can't trade/sell it and
get an 8-10mm ultra wide angle.

I did just order today some Baader solar film to make a proper filter,
going to try to shoot the Venus transit with my best 200mm.


Jon


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Default How do welding shade numbers add up? Eclipse viewing.

On 5/23/2012 1:56 PM, DoN. Nichols wrote:

Did you do what is recommended for mirror lenses -- make a cover
for the front, with a small (say 1" diameter) hole off center so your
actual aperture is significantly smaller that f/11. That might have
gotten you down to f/32 or so. One reason for this is to minimize the
heating of the central mirror which can otherwise be damaged by the heat
from all that sunlight. (And it also lets you use a less dense filter
-- you might have been able to get away with a #10 or so.


I did zero research on the specifics of using this type of lens for
solar photography, only looked into filters and saw some folks were
using #13-#14 welding filters.

BTW -- any idea where the multiple rings on the thin side of the
image came from?


I am not sure, might be an artifact of the design, or perhaps light
reflecting off the back of the welding lens? I know this type of lens
does strange things with out of focus highlights, one gets little rings
of light instead of smooth bokeh. I bought the lens because the price
was certainly right. I saw a couple listed on ebay shortly after I got
it, for over a grand, though in the month I watched them, they didn't
sell. It's a great lens in the right application, but I'm going to
sell/swap it and for an ultra wide angle.


And -- use that off center aperture to cut it down even more and
protect the internal parts of the cat lens.


My main concern and focus on research, was possibly damaging the sensor,
and that sure is an issue w/digital. (hmm, wonder how the folks I saw
driving by one park, fared with their little pocket digital cameras...)
The lens came through it just fine. I've decided if/when I really want
to do astro photography, I'll pick my brother's brain and scope out his rig.

One thing about the Perkin-Elmer lens, is the optics consist of one
solid piece of glass, hence it's name, the Solid Cat. Not sure what
might damage it, unless excess heat on the secondary mirror could damage
the coating. But it survived!


Jon
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Default How do welding shade numbers add up? Eclipse viewing.

That's what I've heard - #14 filter. Welding shop volunteered the
story - they sell out whenever there's an eclipse or something like
that. Lots of non-welding types come by the welding supplies shop.
That was near Cambridge, UK. What with the University, there's a lot
of scientific types around.
RS
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Default How do welding shade numbers add up? Eclipse viewing.

On 2012-05-24, Jon Anderson wrote:
On 5/23/2012 1:56 PM, DoN. Nichols wrote:

Did you do what is recommended for mirror lenses -- make a cover
for the front, with a small (say 1" diameter) hole off center so your
actual aperture is significantly smaller that f/11. That might have


[ ... ]

BTW -- any idea where the multiple rings on the thin side of the
image came from?


I am not sure, might be an artifact of the design, or perhaps light
reflecting off the back of the welding lens? I know this type of lens
does strange things with out of focus highlights, one gets little rings
of light instead of smooth bokeh.


Right -- donut bokeh because of the missing part from the
center.

I bought the lens because the price
was certainly right. I saw a couple listed on ebay shortly after I got
it, for over a grand, though in the month I watched them, they didn't
sell. It's a great lens in the right application, but I'm going to
sell/swap it and for an ultra wide angle.


Hmm ... it might be multiple reflections from the front surface
of the lens and the rear surface of the filter. Or -- if the filter is
multiple layers, and they were not parallel you would get multiple
reflections from that.

[ ... ]

One thing about the Perkin-Elmer lens, is the optics consist of one
solid piece of glass, hence it's name, the Solid Cat. Not sure what
might damage it, unless excess heat on the secondary mirror could damage
the coating. But it survived!


I think that it would be that the heat would soften the typical
adhesives used to attach the center secondary mirror to the back of the
lens. In your case, it appears to have been vacuum evaporated onto the
back, so there is no problem.

BTW You are thinking of parting with the lens you said? What lens
mount? And what are you asking for it?

Enjoy,
DoN.

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Default How do welding shade numbers add up? Eclipse viewing.

On 2012-05-24, Edward A. Falk wrote:
In article ,
Leon Fisk wrote:

Just something to try...

What if you point it at the Sun and then use something like a sparker
(torch lighter, Bic lighter) to trigger it to go dark. Will it stay dark
then, maybe?


Actually, simply waving my hand in front the the sensor was enough to get
it to trigger, but as soon as you stop waving, it goes transparent again.

Tried to think of some flickering light source I could use that I would
trust my vision to, and decided it wasn't a good idea.


Stick a small electric motor and a propeller on the front of the
hood so the propeller interrupts the light to the sensor.

Enjoy,
DoN.

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Default How do welding shade numbers add up? Eclipse viewing.

On 2012-05-26, Jon Anderson wrote:
On 5/25/2012 2:07 PM, DoN. Nichols wrote:

Hmm ... it might be multiple reflections from the front surface


[ ... ]

Used good old duct tape to hold the welding filter to the lens. In
retrospect, I noticed it had shifted a bit as my set progressed, and
wasn't tight against the hood at the end. That could well account for
the multiple reflections.

As to selling, I'll PM that discussion.


O.K. Beware that my address is "spam-proofed", and the
directions on how to fix it are in my .sig below -- which *may* be
hidden by some setting in your newsreader client.

Also -- any e-mails with large attachments (like photos) just
plain won't make it to me. Filtering done on e-mail size to keep
viruses out of a couple of small mailing lists which I host.

Nothing here yet, so I figured that you should be warned of the
limitations in effect.

Thanks,
DoN.

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Default How do welding shade numbers add up? Eclipse viewing.

On 5/25/2012 2:07 PM, DoN. Nichols wrote:

Hmm ... it might be multiple reflections from the front surface
of the lens and the rear surface of the filter. Or -- if the filter is
multiple layers, and they were not parallel you would get multiple
reflections from that.


Used good old duct tape to hold the welding filter to the lens. In
retrospect, I noticed it had shifted a bit as my set progressed, and
wasn't tight against the hood at the end. That could well account for
the multiple reflections.

As to selling, I'll PM that discussion.

Got my Baader solar filter film today, going to machine up a proper
adapter that will thread into my 200mm, insuring it's parallel.


Jon
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Default How do welding shade numbers add up? Eclipse viewing.


"Jon Anderson" wrote in message
news
On 5/25/2012 2:07 PM, DoN. Nichols wrote:

Hmm ... it might be multiple reflections from the front surface
of the lens and the rear surface of the filter. Or -- if the filter is
multiple layers, and they were not parallel you would get multiple
reflections from that.


Used good old duct tape to hold the welding filter to the lens. In
retrospect, I noticed it had shifted a bit as my set progressed, and
wasn't tight against the hood at the end. That could well account for the
multiple reflections.

As to selling, I'll PM that discussion.

Got my Baader solar filter film today, going to machine up a proper
adapter that will thread into my 200mm, insuring it's parallel.


Jon


I do not think the apparent multiple images are reflections. I think it is
just due to the waviness of the filter across the aperture. Each image is
formed by a different area of the filter that has a slightly different wedge
angle. The film works because even though it is wavy, the front and back
surfaces remain very parallel and do not deviate the light.

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Default How do welding shade numbers add up? Eclipse viewing.

On 5/26/2012 1:26 PM, anorton wrote:

I do not think the apparent multiple images are reflections. I think it
is just due to the waviness of the filter across the aperture. Each
image is formed by a different area of the filter that has a slightly
different wedge angle. The film works because even though it is wavy,
the front and back surfaces remain very parallel and do not deviate the
light.


What I hadn't noticed, being behind the camera, was that things got warm
enough for the little bits of duct tape to start slipping. By the end of
my shoot, the welding lens was a couple degrees out, far exceeding any
possible waviness in the filter itself.
In any case, a proper machined holder for the Baader filter is still a
nice thing to have and beats the rolled and glued paper tube the
instructions show...


Jon
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Default How do welding shade numbers add up? Eclipse viewing.


"Jon Anderson" wrote in message
...
On 5/26/2012 1:26 PM, anorton wrote:

I do not think the apparent multiple images are reflections. I think it
is just due to the waviness of the filter across the aperture. Each
image is formed by a different area of the filter that has a slightly
different wedge angle. The film works because even though it is wavy,
the front and back surfaces remain very parallel and do not deviate the
light.


What I hadn't noticed, being behind the camera, was that things got warm
enough for the little bits of duct tape to start slipping. By the end of
my shoot, the welding lens was a couple degrees out, far exceeding any
possible waviness in the filter itself.
In any case, a proper machined holder for the Baader filter is still a
nice thing to have and beats the rolled and glued paper tube the
instructions show...


Jon


But if you you have a flat, parallel piece of glass at an angle in front of
your lens it will not cause any aberration at all for reasonably distant
objects. Even the very dim, double reflection off the inside of the back
surface and then inside of the front surface will overlap perfectly with the
original image for distant objects.



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Default How do welding shade numbers add up? Eclipse viewing.

On 5/26/2012 7:38 PM, anorton wrote:

But if you you have a flat, parallel piece of glass at an angle in front
of your lens it will not cause any aberration at all for reasonably
distant objects. Even the very dim, double reflection off the inside of
the back surface and then inside of the front surface will overlap
perfectly with the original image for distant objects.


Ah, ok. Well, the new filter will use in part, a 55mm filter ring to
thread into the the end of the lens. It's the proper filter, it can be
easily stored, and I don't have to worry about it accidentally falling
off while taking pictures, which the taped filter wanted to do. That's
the main reason for machining a proper setup (as well as keeping a touch
of metalwork in the topic G). I liked the images I got enough to
invest a bit more time to do it properly in the future.

Jon
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Default How do welding shade numbers add up? Eclipse viewing.

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
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Default How do welding shade numbers add up? Eclipse viewing.

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. 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... 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).

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Default How do welding shade numbers add up? Eclipse viewing.

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. 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. 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... 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).


They make/sell filters made to go on the end (Objective) of telescopes.
Usually you have to specify a size, like 90mm or 120 mm depending on
your scope. They are for viewing the Sun. Examples:

https://www.amazon.com/Adjustable-Fi...dp/B071FTTVC5/

https://www.amazon.com/Celestron-Ecl...dp/B000YIXRBW/

https://www.amazon.com/Solar-Filter-...dp/B071671TC1/


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Default How do welding shade numbers add up? Eclipse viewing.

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.

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