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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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  #1  
Old August 21st 17, 07:12 PM posted to uk.tech.digital-tv
Scott[_2_]
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Posts: 1,226
Default Watching an eclipse

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?
  #2  
Old August 21st 17, 07:13 PM posted to uk.tech.digital-tv
Scott[_2_]
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Posts: 1,226
Default Watching an eclipse

On Mon, 21 Aug 2017 20:12:35 +0100, Scott
wrote:

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?

'thought'
  #3  
Old August 21st 17, 07:16 PM posted to uk.tech.digital-tv
Andy Burns[_12_]
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Posts: 346
Default Watching an eclipse

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.



  #4  
Old August 21st 17, 08:03 PM posted to uk.tech.digital-tv
Scott[_2_]
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Posts: 1,226
Default Watching an eclipse

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.
  #5  
Old August 21st 17, 08:09 PM posted to uk.tech.digital-tv
Andy Burns[_12_]
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Posts: 346
Default Watching an eclipse

Scott wrote:

Andy Burns wrote:

special eclipse viewing filters aren't sunglasses.

Okay, but are they safe?


Don't know if you'll find a full version of the relevant ISO standard
without paying the 58 swiss francs, maybe you have a library
subscription that gives access?

https://www.iso.org/obp/ui/#iso:std:59289:en
  #6  
Old August 21st 17, 08:15 PM posted to uk.tech.digital-tv
Peter Duncanson
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Posts: 4,214
Default Watching an eclipse

On Mon, 21 Aug 2017 21:03:08 +0100, Scott
wrote:

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.


Yes, they are safe.
https://eclipse2017.nasa.gov/safety

The only safe way to look directly at the uneclipsed or partially
eclipsed sun is through special-purpose solar filters, such as
“eclipse glasses”

--
Peter Duncanson
(in uk.tech.digital-tv)
  #7  
Old August 21st 17, 08:22 PM posted to uk.tech.digital-tv
Andy Burns[_12_]
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Posts: 346
Default Watching an eclipse

Andy Burns wrote:

Don't know if you'll find a full version of the relevant ISO standard
without paying the 58 swiss francs, maybe you have a library
subscription that gives access?


Doesn't matter where you live, anyone can join the Manchester Central
Library, they give access to the British Standards Online,
and ISO 12312-2 is included within the subscription.

Basically the film must transmit between 0.000061% and 0.0032% of
visible light and no more than 3% of infrared.

  #8  
Old August 21st 17, 09:24 PM posted to uk.tech.digital-tv
Andy Burns[_12_]
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Posts: 346
Default Watching an eclipse

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

https://eclipses.gsfc.nasa.gov/SEpubs/2010/TP214171a.pdf

exposed B&W film provided you know it's a silver-based film

  #9  
Old August 21st 17, 09:37 PM posted to uk.tech.digital-tv
Max Demian
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Posts: 3,783
Default Watching an eclipse

On 21/08/2017 21:15, Peter Duncanson wrote:
On Mon, 21 Aug 2017 21:03:08 +0100, Scott
wrote:

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.


That's what Patrick Moore used to say, presumably in the days before
proper eclipse viewers were available. (They were made available in this
country for the 1999 eclipse. No-one bothered to sell any before.)

Yes, they are safe.
https://eclipse2017.nasa.gov/safety

The only safe way to look directly at the uneclipsed or partially
eclipsed sun is through special-purpose solar filters, such as
“eclipse glasses”


We used to use a dark part of black and white negative film. When a
partial eclipse occurred during a chemistry lesson, our teacher got us
to smoke microscope slides with Bunsen burners before letting us go
outside to watch it.

It's OK unless you do something stupid.

--
Max Demian
  #10  
Old August 22nd 17, 06:44 AM posted to uk.tech.digital-tv
Scott[_2_]
external usenet poster
 
Posts: 1,226
Default Watching an eclipse

On Mon, 21 Aug 2017 22:24:13 +0100, Andy Burns
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

https://eclipses.gsfc.nasa.gov/SEpubs/2010/TP214171a.pdf

exposed B&W film provided you know it's a silver-based film


I was going to ask if such safe methods existed in the 1960s then I
realised there was probably more welding (in the UK) and more
monochorme film in these days :-)
 




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