RASC Hamilton Transit of Venus

Sat May 12 16:12:35 EDT 2012

Odd...Ralph Chou (MSc, OD, Associate Professor, School of Optometry, University of Waterloo and current President of the Toronto Centre) says it's perfectly safe.

http://www.transitofvenus.org/june2012/eye-safety/280-viewing-the-transit-eye-safety

Roger

-----Original Message-----
From: astronomers-bounces at hamiltonrasc.ca on behalf of Andy Blanchard
Sent: Sat 12/05/2012 3:10 PM
To: astronomers at hamiltonrasc.ca
Subject: Re: RASC Hamilton Transit of Venus

There carried on the conversation for a couple of days. The consensus was that the harmfully rays are not blocked by a welders helmet and will cause permanent damage.  The buz was more about the web sites selling its use during the TofV then the question of it's safety. Bottom line don't use it.

Andy Blanchard
905-465-2031H
905-847-7777B

On 2012-05-12, at 12:08 PM, "Roger Hill" <Roger.Hill at hiteach.net> wrote:

> What were the issues?  #14 (no less...#12 is NOT dark enough) stops
> sufficient ultra-violet, visible and infra-red.  The only danger might
> be securely fastening them to the front of a binocular.
> 
> Roger
> 
> -----Original Message-----
> From: astronomers-bounces at hamiltonrasc.ca
> [mailto:astronomers-bounces at hamiltonrasc.ca] On Behalf Of Andy Blanchard
> Sent: Saturday, May 12, 2012 11:48 AM
> To: astronomers at hamiltonrasc.ca
> Subject: Re: RASC Hamilton Transit of Venus
> 
> London just did whole thing on welders glasses and they are clearly too
> dangerous. 
> 
> Andy Blanchard
> 905-465-2031H
> 905-847-7777B
> 
> On 2012-05-12, at 10:34 AM, "Ed Mizzi" <emizzi at cogeco.ca> wrote:
> 
>> Roger,
>> 
>> With the welder's glass, if I secured it to both sides of a pair of
> binoculars would that be safe?
>> 
>> Thanks
>> Ed
>> 
>> 
>> On 2012-05-12, at 9:32 AM, Roger Hill wrote:
>> 
>>> Sorry, Al...I won't be there.  I have my own spot chosen.
>>> 
>>> In 2004, I saw the Sun rise out of Lake Ontario with a big round 
>>> black spot on it.  It was very impressive, and remains one of my 
>>> favourite events (and I've seen three total solar eclipses).
>>> 
>>> I'm going to watch the sun sink down into a lake
>>> 
>>> The Saltfleet site is very good, and will allow some great 
>>> photographs with Venus and tree branches silhouetted against the
> setting sun.
>>> 
>>> One person mentioned solar projection as being safe.  You want to be 
>>> careful what sort of telescope and eyepiece you use for this, 
>>> particularly the eyepiece.  Make sure that the eyepiece is one that 
>>> you don't care about, because the heat build up inside it can ruin 
>>> the glues which hold some lenses together.  Apart from that, it is a
> safe method.
>>> 
>>> What is very definitely NOT (and I cannot stress this enough), is the
> 
>>> use of eyepiece filters.  You used to find them all the time with 
>>> little 60mm refractors sold in the '60's and '70's.  A friend of mine
> 
>>> had one, and we'd used it every now and then for a quick glimpse at 
>>> the sun.  One time, though, we decided to use it to try our hand at 
>>> sketching sunspots. It took less than three minutes to crack. 
>>> Fortunately, it did just as Wayne looked away to start sketching and 
>>> before I got to have a look.
>>> 
>>> What you have is 60mm (or more) of sunlight compressed down into a 
>>> tiny disk, and then compressed even more by the eyepiece.  All of a 
>>> sudden, at the speed of light, all that energy will hit the back of 
>>> your eyeball as the filter cracks...you cannot get out of the way 
>>> fast enough.  There are no pain receptors in the back of your eye, so
> 
>>> it won't be the pain that makes you move out of the way.  There is an
> 
>>> excellent chance that the back of your eye will be permanently 
>>> burned, and you'll see the transit for the rest of your life, forever
> etched in negative.
>>> 
>>> When I do public courses or classes in Astronomy and we get to solar 
>>> observing, I always ask if anyone has one.  I offer to buy it from 
>>> them if they'll bring it to the next class.  It has been quite a few 
>>> years since I saw one, and I'd really hoped that these nasty pieces 
>>> equipment were gone for good.
>>> 
>>> 
>>> Another alternative is #14 welders glass.  This works very well, and 
>>> a
>>> 2x2 piece of it makes an excellent filter for a finder-scope.  Please
> 
>>> make sure that it is secured to the finder, though.  Back in the 
>>> '70's, Johnny Carson show had John Davidson as guest on his show.  
>>> Davidson was also an amateur astronomers (Carson had a C14), and 
>>> mentioned that he'd bought a hydrogen-alpha filter for observing the 
>>> sun.  The views were fantastic, but something didn't smell right, and
> 
>>> he realized that his hair was smouldering, lit by the finder-scope.  
>>> He'd used the projection method to find the Sun (minimize the size of
> 
>>> the shadow of the findersope, and then project the image on to a 
>>> piece of paper to centre it).  He'd forgotten to put a cap on the
> finder-scope.
>>> 
>>> 
>>> Hope this helps,
>>> 
>>> Roger
>>> 
>>> 
>>> -----Original Message-----
>>> From: astronomers-bounces at hamiltonrasc.ca
>>> [mailto:astronomers-bounces at hamiltonrasc.ca] On Behalf Of Al Jones
>>> Sent: Saturday, May 12, 2012 6:00 AM
>>> To: astronomers at hamiltonrasc.ca
>>> Subject: Re: RASC Hamilton Transit of Venus
>>> 
>>> ROGER
>>> Thanks for that advice. I did not realize the mylar was a sharper
> image.
>>> See u at the transit perhaps.
>>> AL
>>> 
>>> On 2012-05-11, at 23:58, "Roger Hill" <Roger.Hill at hiteach.net> wrote:
>>> 
>>>> Al...
>>>> 
>>>> Mylar gives a better image.  I've used both, and while I like the 
>>>> colour that is produced by InCoNel filters, the image is sharper 
>>>> using
>>> mylar.
>>>> 
>>>> Further, since mylar is coated on both sides (the good filters are, 
>>>> anyway), if there is a pinhole or a scratch, it's less likely to go 
>>>> right through.
>>>> 
>>>> Lastly, if you drop the mylar filter, it is far more likely to
>>> survive.
>>>> 
>>>> Roger
>>>> 
>>>> -----Original Message-----
>>>> From: astronomers-bounces at hamiltonrasc.ca
>>>> [mailto:astronomers-bounces at hamiltonrasc.ca] On Behalf Of Al Jones
>>>> Sent: Friday, May 11, 2012 7:41 PM
>>>> To: astronomers at hamiltonrasc.ca
>>>> Subject: RASC Hamilton Transit of Venus
>>>> 
>>>> Hi Gary
>>>> 
>>>> I have a CPC 1100 but no solar filter. I've tried to a get a glass 
>>>> one
>>> 
>>>> from Efston Science but no stock. They said mylar possible but much 
>>>> less durable.
>>>> 
>>>> Suggestions?
>>>> 
>>>> Thx
>>>> 
>>>> Al
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>> 
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