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uk.tech.digital-tv (Digital TV - General) (uk.tech.digital-tv) Discussion of all matters technical in origin related to the reception of digital television transmissions, be they via satellite, terrestrial or cable. Advertising is forbidden, with no exceptions.

Watching an eclipse



 
 
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  #11  
Old August 22nd 17, 06:45 AM posted to uk.tech.digital-tv
Roderick Stewart[_3_]
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Posts: 2,093
Default Watching an eclipse

On 21 Aug 2017 21:54:04 GMT, Huge wrote:

Huge wrote:

I've watched two through (arc) welding filters.


Quite a chunk of the ISO/BS standard is lifted from section 4.1 of this
NASA document


P66;

"One of the most widely available filters for safe solar viewing
is shade number 14 welder’s glass, which can be obtained
from welding supply outlets."


There was a partial eclipse when I was at school in the 1960s which I
watched through a welding filter my Dad had brought home from work. I
remember passing the filter round my classmates, who were suitably
impressed.

However, proper welding filter is probably not readily available to
everyone, and some might be tempted to use sunglasses as a substitute
because superficially they appear to do the same thing, so Patrick
Moore's warning about only using a pinhole device is probably good
general advice. No matter what advice you give to the public, some
won't listen, some won't understand it, some will ignore it, and some
will think they know better.

Rod.
  #12  
Old August 22nd 17, 07:28 AM posted to uk.tech.digital-tv
Brian Gaff
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Posts: 6,757
Default Watching an eclipse

If they have the right filter material its fine. It did cross my mind though
that if there were cheap Japanese copies floating about there will be a lot
of people with blind spots this morning.
I forget the filter used but you used to be able to get the material at
good old camera shops for a very high price.

Brian

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"Scott" wrote in message
...
I have just seen coverage on Channel 4 News of the eclipse, where
people were watching using special sunglasses. I though no sunglasses
were safe for looking directly at the sun?



  #13  
Old August 22nd 17, 07:30 AM posted to uk.tech.digital-tv
Brian Gaff
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Posts: 6,757
Default Watching an eclipse

Though you can build them into viewing glasses like anything else. The most
misconceived thing is to use welders goggles. these do not protect your
eyes against a wide enough frequency range.
Brian

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"Andy Burns" wrote in message
...
Scott wrote:

people were watching using special sunglasses. I though no sunglasses
were safe for looking directly at the sun?


special eclipse viewing filters aren't sunglasses.





  #14  
Old August 22nd 17, 07:32 AM posted to uk.tech.digital-tv
Brian Gaff
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Posts: 6,757
Default Watching an eclipse

No that is wrong. I think the point is, unless the material is certified for
the direct viewing of the sun, its probably no good and should be avoided.

Brian

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"Scott" wrote in message
...
On Mon, 21 Aug 2017 20:16:09 +0100, Andy Burns
wrote:

Scott wrote:

people were watching using special sunglasses. I though no sunglasses
were safe for looking directly at the sun?


special eclipse viewing filters aren't sunglasses.

Okay, but are they safe? I was taught as a child that NO device was
safe to look directly at the sun and the ONLY way to watch an eclipse
safely was via a pinhole projecting on to a sheet of paper.



  #16  
Old August 22nd 17, 07:34 AM posted to uk.tech.digital-tv
NY
external usenet poster
 
Posts: 1,135
Default Watching an eclipse

"Roderick Stewart" wrote in message
...
"One of the most widely available filters for safe solar viewing
is shade number 14 welder's glass, which can be obtained
from welding supply outlets."


There was a partial eclipse when I was at school in the 1960s which I
watched through a welding filter my Dad had brought home from work. I
remember passing the filter round my classmates, who were suitably
impressed.

However, proper welding filter is probably not readily available to
everyone, and some might be tempted to use sunglasses as a substitute
because superficially they appear to do the same thing, so Patrick
Moore's warning about only using a pinhole device is probably good
general advice. No matter what advice you give to the public, some
won't listen, some won't understand it, some will ignore it, and some
will think they know better.


During the UK eclipse in the 1990s, some people at the computer company
where I worked watched the sun through the magnetic floppy part of a floppy
disk. 5 1/4" discs are easier to dismantle than 3 1/2" diskettes to do this.
I never even knew that the magnetic surface was transparent enough to be
able to see a bright light through it.

  #17  
Old August 22nd 17, 11:04 AM posted to uk.tech.digital-tv
Indy Jess John
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Posts: 1,180
Default Watching an eclipse

On 21/08/2017 22:37, Max Demian wrote:

We used to use a dark part of black and white negative film.


I did something similar for the first eclipse I saw, putting five Black
& White photographic negatives together then viewing through them.

It was a little bit patchy, but safe enough, varying between dark enough
and too dark.

The second time I saw an eclipse was in the 1980s and I watched it as a
reflection in the water in a Fire Bucket at the place I was working at.

Jim
  #18  
Old August 22nd 17, 12:23 PM posted to uk.tech.digital-tv
Max Demian
external usenet poster
 
Posts: 3,783
Default Watching an eclipse

On 22/08/2017 12:04, Indy Jess John wrote:
On 21/08/2017 22:37, Max Demian wrote:

We used to use a dark part of black and white negative film.


I did something similar for the first eclipse I saw, putting five Black
& White photographic negatives together then viewing through them.

It was a little bit patchy, but safe enough, varying between dark enough
and too dark.

The second time I saw an eclipse was in the 1980s and I watched it as a
reflection in the water in a Fire Bucket at the place I was working at.


For the 1999 eclipse, 'experts' advised that we watch it on TV. And they
advised the same about the millennium fireworks in London ('cos of all
the crowds I think). They obviously hadn't got the hang of this
'reality' thing,

--
Max Demian
  #19  
Old August 22nd 17, 12:25 PM posted to uk.tech.digital-tv
Max Demian
external usenet poster
 
Posts: 3,783
Default Watching an eclipse

On 22/08/2017 07:45, Roderick Stewart wrote:
On 21 Aug 2017 21:54:04 GMT, Huge wrote:

Huge wrote:

I've watched two through (arc) welding filters.

Quite a chunk of the ISO/BS standard is lifted from section 4.1 of this
NASA document


P66;

"One of the most widely available filters for safe solar viewing
is shade number 14 welder’s glass, which can be obtained
from welding supply outlets."


There was a partial eclipse when I was at school in the 1960s which I
watched through a welding filter my Dad had brought home from work. I
remember passing the filter round my classmates, who were suitably
impressed.

However, proper welding filter is probably not readily available to
everyone, and some might be tempted to use sunglasses as a substitute
because superficially they appear to do the same thing, so Patrick
Moore's warning about only using a pinhole device is probably good
general advice. No matter what advice you give to the public, some
won't listen, some won't understand it, some will ignore it, and some
will think they know better.


So why say, "Don't use sunglasses"?

--
Max Demian
  #20  
Old August 22nd 17, 12:32 PM posted to uk.tech.digital-tv
Max Demian
external usenet poster
 
Posts: 3,783
Default Watching an eclipse

On 22/08/2017 08:32, Brian Gaff wrote:
No that is wrong. I think the point is, unless the material is certified for
the direct viewing of the sun, its probably no good and should be avoided.


What does 'certified' mean? Mine (useless for yesterday evening's cloudy
aspect needless to say) say "Safe Solar Viewers" and have a CE symbol in
the middle. But anyone can print that. In the end (as with most things)
you have no option but to rely on your own experience and common sense.

--
Max Demian
 




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