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  #41  
Old 09.03.2015, 13:22
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Re: Solar eclipse

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Looking at the sun through water reflection is similar to looking at the sun directly with normal sunglasses, something I think most sensible people would agree is pretty dumb.
Of course most people would agree that it is pretty dumb, but IF and ONLY IF, looking at the sun through water reflection is similar to looking at the sun directly with normal sunglasses, which appears not to have been demonstrated.

Infrared light is not well reflected by water, it tends to get absorbed. The problems caused by looking directly at the sun are mostly attributable to visible light intensity. It is photochemical not thermal.
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  #42  
Old 09.03.2015, 14:07
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Re: Solar eclipse

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Of course most people would agree that it is pretty dumb, but IF and ONLY IF, looking at the sun through water reflection is similar to looking at the sun directly with normal sunglasses, which appears not to have been demonstrated.

Infrared light is not well reflected by water, it tends to get absorbed. The problems caused by looking directly at the sun are mostly attributable to visible light intensity. It is photochemical not thermal.
Ok, let's throw away the infra-red and just look at visible (which we know can cause damage in sufficient amounts). What's a typical transmission rate of sunglasses? Somewhere between 25% and 10%? What's the albedo of water? Depending on sun height, between 3% and 10%. How safe do you feel?

And I'll repeat this: every recommendation for how you should safely view an eclipse has multiple orders of magnitude less light transmission than water reflection. Again, how safe do you feel? How safe would you feel getting a child to do this? (The original poster actually recommended this practice for children).

Here's some information from a Nasa site (http://eclipse.gsfc.nasa.gov/SEhelp/safety2.html):

The Sun can only be viewed directly when filters specially designed to protect the eyes are used. Most such filters have a thin layer of chromium alloy or aluminum deposited on their surfaces that attenuates both visible and near-infrared radiation. A safe solar filter should transmit less than 0.003% (density~4.5)[1] of visible light (380 to 780 nm)

They specify less than 0.003%; water is at least 3%. Do you really want to keep arguing this?
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  #43  
Old 09.03.2015, 14:47
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Re: Solar eclipse

Apart from the fact that watching the sun by reflection on the water is a very dumb thing indeed, how do those who promote it get the water surface absolutely undisturbed?

That would need a separate, completely sealed room for the water, with windows both on the side of the sun and on the side of the observer. Not even a hint of draft, no truck, train or tram passing by at less than, say, 200 yards, window panes preferably equipped with antireflective coating to reduce glare and double images, and, of course, no one inside the room.

Then, and only then, you'd be able to get a glimpse of the eclipse before your eyes get damaged. Even the slightest ripple, caused by a flea burping nearby, would make proper observation impossible.

I guess it's simpler to get a proper filter. Even constructing a pinhole camera is more convenient, although it provides only kind of a second-hand experience.
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  #44  
Old 09.03.2015, 18:42
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Re: Solar eclipse

Thanks for all the info everyone! I have got myself a 14 welders glass
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  #45  
Old 09.03.2015, 18:58
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Re: Solar eclipse

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Ok, let's throw away the infra-red and just look at visible (which we know can cause damage in sufficient amounts). What's a typical transmission rate of sunglasses? Somewhere between 25% and 10%? What's the albedo of water? Depending on sun height, between 3% and 10%. How safe do you feel?

And I'll repeat this: every recommendation for how you should safely view an eclipse has multiple orders of magnitude less light transmission than water reflection. Again, how safe do you feel? How safe would you feel getting a child to do this? (The original poster actually recommended this practice for children).

Here's some information from a Nasa site (http://eclipse.gsfc.nasa.gov/SEhelp/safety2.html):

The Sun can only be viewed directly when filters specially designed to protect the eyes are used. Most such filters have a thin layer of chromium alloy or aluminum deposited on their surfaces that attenuates both visible and near-infrared radiation. A safe solar filter should transmit less than 0.003% (density~4.5)[1] of visible light (380 to 780 nm)

They specify less than 0.003%; water is at least 3%. Do you really want to keep arguing this?
You ridicule SBrinz, then come up with a bunch of reasons why you are right, which I've shown are not true. Looking at the sun via water reflection is not looking at the sun directly and doesn't seem to be included (or excluded) in the official advice given viewers.

Your quote from NASA is irrelevant, since viewing the eclipse via reflection is not viewing the Sun directly.

I wouldn't recommend it myself; I've already made that quite clear. Hope that makes it entirely clear for you.
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  #46  
Old 10.03.2015, 09:33
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Re: Solar eclipse

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You ridicule SBrinz, then come up with a bunch of reasons why you are right, which I've shown are not true. Looking at the sun via water reflection is not looking at the sun directly and doesn't seem to be included (or excluded) in the official advice given viewers.

Your quote from NASA is irrelevant, since viewing the eclipse via reflection is not viewing the Sun directly.

I wouldn't recommend it myself; I've already made that quite clear. Hope that makes it entirely clear for you.
Incredible. You really can't let it lie, can you? Yes, I ridiculed SBrinz (well deserved, particularly since that post hasn't been edited to say that this is not a safe practice) and I'll ridicule you, too.

I'd really rather not continue in this pointless back-and-forth but will because I don't want anybody to get the idea that the "reflection loonies" somehow have any kind of case.

You points seem to be:

1) Nasa don't explicitly forbid it. In fact, nobody forbids it.

2) People were doing it a 1000 years ago and they're fine!

3) Reflection is not the same as direct viewing.

4) I haven't show it.

So:

1) Nasa give explicit advice for how to view an eclipse. I think we can assume that anything outside this is not advised. Plenty of eclipse guides say that this is not a safe practice. E.g. the eso.org guide says:

I’ve heard some daft ideas for eclipse viewing, such as looking through a sheet of Perspex, or in a reflection in a bucket of water. I have no idea where these come from, but these are not safe!

2) I think we covered that. In terms of physics and physiology, we're just so much smarter than them.

3) Do you somehow think that in the process of reflection (absorption and emission of a photon), the emitted photon is somehow magic pixie dust which doesn't have any detrimental organic effects? Of course not, the process of reflection in water does some filtering of the wavelengths and returns about 3% of the light intensity. Photons are photons. To push this point further: would you think it's safe to view a solar eclipse in a mirror reflection?

4) Yes I have! Let me repeat: A safe solar filter should transmit less than 0.003% (density~4.5)[1] of visible light (380 to 780 nm). Given (3), we can say that this advice means: Don't stare at more that 0.003% of the sun's intensity!

Consider yourself ridiculed.
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  #47  
Old 10.03.2015, 10:02
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Re: Solar eclipse

But but but some bloke on the Internet says I can use foil and water and because they did that in China everything is fine.
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  #48  
Old 10.03.2015, 10:31
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Re: Solar eclipse

I think what everyone is referring to is that viewing the sun from Earth can be hazardous. Now if you were to look at the Dark Side of the Sun .....
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  #49  
Old 18.03.2015, 14:41
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Re: Solar eclipse

Hi All,

does anyone know if one can still buy any Solar eclipse glasses in Zurich, from where and at what cost?

Thnaks
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  #50  
Old 18.03.2015, 14:43
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Re: Solar eclipse

Samsung 3D glasses should work a treat.
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Old 18.03.2015, 14:46
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Re: Solar eclipse

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Samsung 3D glasses should work a treat.
Nope, that does not work. they are too light on the dark colour!
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Old 18.03.2015, 15:06
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Re: Solar eclipse

I think in 1999, stood on Parliament Hill, I used three pairs of sunglasses, together.

I was very disappointed that it didn't seem to go particularly dark, where I was, though - just a bit like a dull, cloudy evening.
I was even able to video it - got a tape, somewhere.
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  #53  
Old 18.03.2015, 15:27
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Re: Solar eclipse

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Apart from the fact that watching the sun by reflection on the water is a very dumb thing indeed, how do those who promote it get the water surface absolutely undisturbed?
i recommend a pool of mercury instead of water.
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Old 18.03.2015, 17:11
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Re: Solar eclipse

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Samsung 3D glasses should work a treat.
good grief haha!
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Old 18.03.2015, 17:15
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Re: Solar eclipse

Practised my eclipse photography today with my phone and the welders glass! We have a good view from our balcony during the eclipse hours
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  #56  
Old 18.03.2015, 17:16
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Re: Solar eclipse

this was holding the glass infront of the cameraabout 10cm maybe it would be better if I held the glass against the back of the phone? notice it looks a bit warped on the right
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  #57  
Old 18.03.2015, 17:39
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Re: Solar eclipse

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Water itself has a low albedo.
Apparently Viagra helps with this problem.
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Old 18.03.2015, 18:10
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Re: Solar eclipse

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i recommend a pool of mercury instead of water.
Unfortunately, in this instance, Mercury will be nowhere near the sun.
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Old 19.03.2015, 18:59
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Re: Solar eclipse

unbelievable that all the special glasses to watch the eclipse are sold out everywhere in Zürich. What a s**t!
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Old 19.03.2015, 19:06
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Re: Solar eclipse

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unbelievable that all the special glasses to watch the eclipse are sold out everywhere in Zürich. What a s**t!
Another example of missed opportunity to make a mint, ripping off Joe Public. It was the same in Bern ..... last week, already.
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