Roger that was an informative and hilarious answer.<div><br>I love the part about seeing the transit permanently, and the smouldering hair.</div><div><br></div><div>So if I hear you correctly, in addition to the filter (glass or mylar), do I need to ensure a different eyepiece? This begs the question, is solar observing simply hard on telescope because of the heat involved?</div>
<div><br></div><div><br></div><div>Thanks,</div><div><br></div><div>Al</div><div><br></div><div><br></div><div><br></div><div><br><br><div class="gmail_quote">On Sat, May 12, 2012 at 9:32 AM, Roger Hill <span dir="ltr"><<a href="mailto:Roger.Hill@hiteach.net" target="_blank">Roger.Hill@hiteach.net</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Sorry, Al...I won't be there. I have my own spot chosen.<br>
<br>
In 2004, I saw the Sun rise out of Lake Ontario with a big round black<br>
spot on it. It was very impressive, and remains one of my favourite<br>
events (and I've seen three total solar eclipses).<br>
<br>
I'm going to watch the sun sink down into a lake<br>
<br>
The Saltfleet site is very good, and will allow some great photographs<br>
with Venus and tree branches silhouetted against the setting sun.<br>
<br>
One person mentioned solar projection as being safe. You want to be<br>
careful what sort of telescope and eyepiece you use for this,<br>
particularly the eyepiece. Make sure that the eyepiece is one that you<br>
don't care about, because the heat build up inside it can ruin the glues<br>
which hold some lenses together. Apart from that, it is a safe method.<br>
<br>
What is very definitely NOT (and I cannot stress this enough), is the<br>
use of eyepiece filters. You used to find them all the time with little<br>
60mm refractors sold in the '60's and '70's. A friend of mine had one,<br>
and we'd used it every now and then for a quick glimpse at the sun. One<br>
time, though, we decided to use it to try our hand at sketching<br>
sunspots. It took less than three minutes to crack. Fortunately, it did<br>
just as Wayne looked away to start sketching and before I got to have a<br>
look.<br>
<br>
What you have is 60mm (or more) of sunlight compressed down into a tiny<br>
disk, and then compressed even more by the eyepiece. All of a sudden,<br>
at the speed of light, all that energy will hit the back of your eyeball<br>
as the filter cracks...you cannot get out of the way fast enough. There<br>
are no pain receptors in the back of your eye, so it won't be the pain<br>
that makes you move out of the way. There is an excellent chance that<br>
the back of your eye will be permanently burned, and you'll see the<br>
transit for the rest of your life, forever etched in negative.<br>
<br>
When I do public courses or classes in Astronomy and we get to solar<br>
observing, I always ask if anyone has one. I offer to buy it from them<br>
if they'll bring it to the next class. It has been quite a few years<br>
since I saw one, and I'd really hoped that these nasty pieces equipment<br>
were gone for good.<br>
<br>
<br>
Another alternative is #14 welders glass. This works very well, and a<br>
2x2 piece of it makes an excellent filter for a finder-scope. Please<br>
make sure that it is secured to the finder, though. Back in the '70's,<br>
Johnny Carson show had John Davidson as guest on his show. Davidson was<br>
also an amateur astronomers (Carson had a C14), and mentioned that he'd<br>
bought a hydrogen-alpha filter for observing the sun. The views were<br>
fantastic, but something didn't smell right, and he realized that his<br>
hair was smouldering, lit by the finder-scope. He'd used the projection<br>
method to find the Sun (minimize the size of the shadow of the<br>
findersope, and then project the image on to a piece of paper to centre<br>
it). He'd forgotten to put a cap on the finder-scope.<br>
<br>
<br>
Hope this helps,<br>
<div class="im HOEnZb"><br>
Roger<br>
<br>
<br>
-----Original Message-----<br>
From: <a href="mailto:astronomers-bounces@hamiltonrasc.ca">astronomers-bounces@hamiltonrasc.ca</a><br>
[mailto:<a href="mailto:astronomers-bounces@hamiltonrasc.ca">astronomers-bounces@hamiltonrasc.ca</a>] On Behalf Of Al Jones<br>
</div><div class="im HOEnZb">Sent: Saturday, May 12, 2012 6:00 AM<br>
</div><div class="HOEnZb"><div class="h5">To: <a href="mailto:astronomers@hamiltonrasc.ca">astronomers@hamiltonrasc.ca</a><br>
Subject: Re: RASC Hamilton Transit of Venus<br>
<br>
ROGER<br>
Thanks for that advice. I did not realize the mylar was a sharper image.<br>
See u at the transit perhaps.<br>
AL<br>
<br>
On 2012-05-11, at 23:58, "Roger Hill" <<a href="mailto:Roger.Hill@hiteach.net">Roger.Hill@hiteach.net</a>> wrote:<br>
<br>
> Al...<br>
><br>
> Mylar gives a better image. I've used both, and while I like the<br>
> colour that is produced by InCoNel filters, the image is sharper using<br>
mylar.<br>
><br>
> Further, since mylar is coated on both sides (the good filters are,<br>
> anyway), if there is a pinhole or a scratch, it's less likely to go<br>
> right through.<br>
><br>
> Lastly, if you drop the mylar filter, it is far more likely to<br>
survive.<br>
><br>
> Roger<br>
><br>
> -----Original Message-----<br>
> From: <a href="mailto:astronomers-bounces@hamiltonrasc.ca">astronomers-bounces@hamiltonrasc.ca</a><br>
> [mailto:<a href="mailto:astronomers-bounces@hamiltonrasc.ca">astronomers-bounces@hamiltonrasc.ca</a>] On Behalf Of Al Jones<br>
> Sent: Friday, May 11, 2012 7:41 PM<br>
> To: <a href="mailto:astronomers@hamiltonrasc.ca">astronomers@hamiltonrasc.ca</a><br>
> Subject: RASC Hamilton Transit of Venus<br>
><br>
> Hi Gary<br>
><br>
> I have a CPC 1100 but no solar filter. I've tried to a get a glass one<br>
<br>
> from Efston Science but no stock. They said mylar possible but much<br>
> less durable.<br>
><br>
> Suggestions?<br>
><br>
> Thx<br>
><br>
> Al<br>
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