Over exposed dental x-ray film for observing an eclipse?

[W. eWatson]

Will overexposed x-ray film work for viewing an a solar eclipse, or just
observing the sun?

[Chris L Peterson]

I wouldn't trust any photographic film for viewing the Sun. Its
relative safety in the past was based on its use of silver in the
emulsion, but most modern films use more complex dye chemistries now,
and that includes some x-ray film.

Why take a chance? Aluminized Mylar and similar metal coated films
designed just for solar viewing are readily available for free or
cheap (easier to get than processed x-ray film). There's no reason not
to use the better materials.

Of course, when viewing a non-annular total eclipse at totality, you
don't want to use any filter at all. Annular and partial eclipses
require filters.

[lal_truckee]

On 2/7/12 1:50 PM, W. eWatson wrote:
> Will overexposed x-ray film work for viewing an a solar eclipse, or just
> observing the sun?

See the "Glasses" for the Annular Eclipse on May 20th" thread just above
for sources of proper solar filters cheap.

[Martin Brown]

W. eWatson wrote:
> Will overexposed x-ray film work for viewing an a solar eclipse, or just
> observing the sun?

Only *iff* it is silver halide rather than organic dye based chemistry.

The latter will look plenty dark enough and make the image comfortably
bright whilst allowing almost undimished infrared through to fry your
eyeball. There are no immediate pain receptors in the eye so you do not
notice until much later.

Scars shaped like a cresecent or donut are a real possibility in the
later stages of an eclipse. The last bit of photosphere is still at
5000K but your eye is wide open and the eye cannot cope with the thermal
load that puts on the retina. The damage and pain develops a few hours
later.

The ill fated Belgian physicist Plateau reportedly made himself blind in
one eye by staring fixedly at the sun for about 25 seconds.

It really isn't worth taking a chance. Bader solar film is reliable.

Regards,
Martin Brown

[William Hamblen]

On 2012-02-07, W. eWatson <wolft...@invalid.com> wrote:
> Will overexposed x-ray film work for viewing an a solar eclipse, or just
> observing the sun?

Where are you going to get it? Medical and dental X-rays are now digital.
I learned that when I got x-rayed last year. No film.

In any case, I wouldn't use it.

Bud

[W. eWatson]

Duly noted the above. I ordered 25 cards from 1000 Oaks per my post
above on Annular Eclipse.

[W. eWatson]

Often welder's glass is suggested. Where would one get a small piece?
2x4". I'm really aiming at distant individuals I know who do not know
about these matters. That is, I would like to recommend material they
can easily buy to protect there eyes, but at a low cost.

[Bill Owen]

W. eWatson wrote:
> Will overexposed x-ray film work for viewing an a solar eclipse, or just
> observing the sun?

http://eclipse.gsfc.nasa.gov/SEhelp/safety2.html
says that black-and-white film is safe if it uses silver halide instead
of dyes and if it's been suitably overexposed. (I'm paraphrasing.)

Nevertheless, I wouldn't bet my eyes on it. Use aluminized mylar or #14
welder's glass for direct viewing, or pinhole projection.

-- Bill Owen

[Chris L Peterson]

On Tue, 07 Feb 2012 14:41:33 -0800, "W. eWatson"
<wolft...@invalid.com> wrote:

>Often welder's glass is suggested. Where would one get a small piece?
>2x4". I'm really aiming at distant individuals I know who do not know
>about these matters. That is, I would like to recommend material they
>can easily buy to protect there eyes, but at a low cost.

You can get it online, and you can get it from places that sell
welding supplies. One small piece of #14 welder's glass will cost
about the same as your pack of 25 eclipse cards, and won't be of as
good optical quality. And it would be quite easy to end up with
something like #10 glass, which lets a dangerous amount of light
through.

I really can't think of why anybody can't use eclipse glasses or cards
designed for that purpose. They're cheaper, they're easier to get, and
they work better.

[Sjouke Burry]

"W. eWatson" <wolft...@invalid.com> wrote in
news:jgs9b0$2pk$1...@dont-email.me:

I use my tripple layer sunfilter from my telescope.
A metal layer(not the writable ones)audio CD also works rather well.
And old floppys performed wel also.

[wsne...@hotmail.com]

On Feb 7, 5:41 pm, "W. eWatson" <wolftra...@invalid.com> wrote:
> On 2/7/2012 2:32 PM, W. eWatson wrote:
>
> > On 2/7/2012 2:21 PM, William Hamblen wrote:

> >> On 2012-02-07, W. eWatson<wolftra...@invalid.com> wrote:
> >>> Will overexposed x-ray film work for viewing an a solar eclipse, or just
> >>> observing the sun?
>
> >> Where are you going to get it? Medical and dental X-rays are now digital.
> >> I learned that when I got x-rayed last year. No film.
>
> >> In any case, I wouldn't use it.
>
> >> Bud
>
> > Duly noted the above. I ordered 25 cards from 1000 Oaks per my post
> > above on Annular Eclipse.
>
> Often welder's glass is suggested. Where would one get a small piece?
> 2x4". I'm really aiming at distant individuals I know who do not know
> about these matters. That is, I would like to recommend material they
> can easily buy to protect there eyes, but at a low cost.

Don't use those. Stick with the material designed and meant for safe
viewing.

You could try a pinhole reflector, which would be useful for eclipse
viewing by a group. Cover a mirror with heavy paper or cardboard that
has a 1/8-inch or smaller hole. Reflect the Sun's light into a
darkened room through an open door or window onto a screen or light-
colored wall. A larger distance and/or smaller hole gives a
sharper, but dimmer image. A first-surface mirror is ideal but second-
surface should be OK.

[W. eWatson]

You are right about welding supplies. I could buy a 4x6" #11 sheet for
about $3.70. I suspect one could easily cut it up for use by several
people.

The problem with eclipse cards, and cards, AFIK, is they aren't sold
singly. It's been raining here all day, and tomorrow it should be sunny,
so I'm going back to the welding supplier and try out #14 and check the
cost. The clerk was fascinated by the use, so maybe we'll see some sun
spots.

[W. eWatson]

Hi, Bill. See my response to Chris P above. It looks like #14 is the way
to go in some cases, but for sky show efforts, I can see a combination,
and particularly the use of the cards. Projections are good way too to
fulfill needs of a large # of people. Wayne Watson

[Chris L Peterson]

On Tue, 07 Feb 2012 17:34:45 -0800, "W. eWatson"
<wolft...@invalid.com> wrote:

>The problem with eclipse cards, and cards, AFIK, is they aren't sold
>singly.

Sure they are. http://www.rainbowsymphonystore.com/eclipseshades.html
is just one place that sells them singly, and dirt cheap.

[Odysseus]

In article <nv73j75hkaf8qrvo0...@4ax.com>,

Chris L Peterson <c...@alumni.caltech.edu> wrote:

> On Tue, 07 Feb 2012 13:50:10 -0800, "W. eWatson"
> <wolft...@invalid.com> wrote:
>
> >Will overexposed x-ray film work for viewing an a solar eclipse, or just
> >observing the sun?
>
> I wouldn't trust any photographic film for viewing the Sun. Its
> relative safety in the past was based on its use of silver in the
> emulsion, but most modern films use more complex dye chemistries now,
> and that includes some x-ray film.

High-contrast litho film is safe enough, but I'd advise using two
layers: not only to increase the optical density, but in case of defects
in the emulsion. Pinhole projection or reflection is definitely tne
safest method of observing the Sun without purpose-made gear.

--
Odysseus

[William Hamblen]

On 2012-02-08, W. eWatson <wolft...@invalid.com> wrote:
> On 2/7/2012 3:07 PM, Chris L Peterson wrote:
>> On Tue, 07 Feb 2012 14:41:33 -0800, "W. eWatson"
>> <wolft...@invalid.com> wrote:
>>
>>> Often welder's glass is suggested. Where would one get a small piece?
>>> 2x4". I'm really aiming at distant individuals I know who do not know
>>> about these matters. That is, I would like to recommend material they
>>> can easily buy to protect there eyes, but at a low cost.
>>
>> You can get it online, and you can get it from places that sell
>> welding supplies. One small piece of #14 welder's glass will cost
>> about the same as your pack of 25 eclipse cards, and won't be of as
>> good optical quality. And it would be quite easy to end up with
>> something like #10 glass, which lets a dangerous amount of light
>> through.
>>
>> I really can't think of why anybody can't use eclipse glasses or cards
>> designed for that purpose. They're cheaper, they're easier to get, and
>> they work better.
> You are right about welding supplies. I could buy a 4x6" #11 sheet for
> about $3.70. I suspect one could easily cut it up for use by several
> people.

Eleven shade isn't dense enough. Use 14 shade only. Industrial suppliers
don't stock it because there is not much call for so dense a shade. You
need to special order.

Bud

[wsne...@hotmail.com]

On Feb 8, 5:00 am, William Hamblen <william.hamb...@earthlink.net>
wrote:

> On 2012-02-08, W. eWatson <wolftra...@invalid.com> wrote:
>
>
>
>
>
> > On 2/7/2012 3:07 PM, Chris L Peterson wrote:
> >> On Tue, 07 Feb 2012 14:41:33 -0800, "W. eWatson"

> >> <wolftra...@invalid.com>  wrote:

>
> >>> Often welder's glass is suggested. Where would one get a small piece?
> >>> 2x4". I'm really aiming at distant individuals I know who do not know
> >>> about these matters. That is, I would like to recommend material they
> >>> can easily buy to protect there eyes, but at a low cost.
>
> >> You can get it online, and you can get it from places that sell
> >> welding supplies. One small piece of #14 welder's glass will cost
> >> about the same as your pack of 25 eclipse cards, and won't be of as
> >> good optical quality. And it would be quite easy to end up with
> >> something like #10 glass, which lets a dangerous amount of light
> >> through.
>
> >> I really can't think of why anybody can't use eclipse glasses or cards
> >> designed for that purpose. They're cheaper, they're easier to get, and
> >> they work better.
> > You are right about welding supplies. I could buy a 4x6" #11 sheet for
> > about $3.70.  I suspect one could easily cut it up for use by several
> > people.
>
> Eleven shade isn't dense enough.  Use 14 shade only.  Industrial suppliers
> don't stock it because there is not much call for so dense a shade.  You
> need to special order.

So why not just order the safe, proven, tested product instead?

(If one suggests using something else, the liberals are likely to
select the wrong thing to use and end up causing injury to themselves
or others.)

[W. eWatson]

Postage and Handling?

As it turns out our welding supplier sells a #14 for $1.87. I'll wait
until I get back from a long trip before ordering one. They had none
available. I can cut into 3 or 4 pieces.