RASC Hamilton Transit of Venus

[Ed Mizzi]

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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