Sounds like the name of the game is talking to people who are in the know ...<div><br></div><div>Seems fraught with ideas like that ofDaedalusand Icarus</div><div><br></div><div>Thanks again for saving my eyeballs</div><div>
<br></div><div><br></div><div><br><br><div class="gmail_quote">On Sat, May 12, 2012 at 9:58 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"><div lang="EN-US" link="blue" vlink="purple"><div><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">If you use a front of the objective filter, then nothing else is needed just make sure that it is securely fastend and the wind wont blow it off. Get the good Baader filter material, as its coated on both sides. You can then use any eyepiece you want, as the light coming through is cut down to 1/100,000<sup>th</sup> of what it normally is, which is the right brightness level. Putting a hood, or towel, over your head to block out any extraneous light is also a good idea.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">So yes, solar observing is almost all about making sure that energy is rejected. Absorbing it, as the eyepiece filters do, is not good practice. <u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">There are some eyepiece filters (the highly specialized, expensive, sub-angstrom Hydrogen Alpha type) that are safe, but only if accompanied by a front-mounted Energy Rejection Filter.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">One other caveat. Some people have used the NASA Solar blanket material, but this is NOT SAFE. It was tested by Dr. Ralph Chu (current President of the Toronto Centre), a research ophthalmologist and found that it transmits too much ultra-violet and infra-red. This is really nasty, as it will cook your eyeball and you wont even realize it, because it doesnt appear to be too bright. This stuff is not checked for the thickness of the coating, and therefore varies wildly in brightness and optical quality. I used it for a brief time before I heard about Ralphs research, and while it seemed to provide safety, there was something about it that didnt feel right. I was lucky. <u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Which is why I said almost earlier, as you must also ensure that only visible light gets through.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Roger<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u><u></u></span></p><div style="border:none;border-top:solid #b5c4df 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> <a href="mailto:astronomers-bounces@hamiltonrasc.ca" target="_blank">astronomers-bounces@hamiltonrasc.ca</a> [mailto:<a href="mailto:astronomers-bounces@hamiltonrasc.ca" target="_blank">astronomers-bounces@hamiltonrasc.ca</a>] <b>On Behalf Of </b>Al Jones<br>
<b>Sent:</b> Saturday, May 12, 2012 9:39 AM</span></p><div><div class="h5"><br><b>To:</b> <a href="mailto:astronomers@hamiltonrasc.ca" target="_blank">astronomers@hamiltonrasc.ca</a><br><b>Subject:</b> Re: RASC Hamilton Transit of Venus<u></u><u></u></div>
</div><p></p></div><div><div class="h5"><p class="MsoNormal"><u></u><u></u></p><p class="MsoNormal">Roger that was an informative and hilarious answer.<u></u><u></u></p><div><p class="MsoNormal"><br>I love the part about seeing the transit permanently, and the smouldering hair.<u></u><u></u></p>
</div><div><p class="MsoNormal"><u></u><u></u></p></div><div><p class="MsoNormal">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?<u></u><u></u></p>
</div><div><p class="MsoNormal"><u></u><u></u></p></div><div><p class="MsoNormal"><u></u><u></u></p></div><div><p class="MsoNormal">Thanks,<u></u><u></u></p></div><div><p class="MsoNormal"><u></u><u></u></p></div><div>
<p class="MsoNormal">Al<u></u><u></u></p></div><div><p class="MsoNormal"><u></u><u></u></p></div><div><p class="MsoNormal"><u></u><u></u></p></div><div><p class="MsoNormal"><u></u><u></u></p></div><div><p class="MsoNormal" style="margin-bottom:12.0pt">
<u></u><u></u></p><div><p class="MsoNormal">On Sat, May 12, 2012 at 9:32 AM, Roger Hill <<a href="mailto:Roger.Hill@hiteach.net" target="_blank">Roger.Hill@hiteach.net</a>> wrote:<u></u><u></u></p><p class="MsoNormal">
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,<u></u><u></u></p><div><p class="MsoNormal"><br>Roger<br><br>
<br>-----Original Message-----<br>From: <a href="mailto:astronomers-bounces@hamiltonrasc.ca" target="_blank">astronomers-bounces@hamiltonrasc.ca</a><br>[mailto:<a href="mailto:astronomers-bounces@hamiltonrasc.ca" target="_blank">astronomers-bounces@hamiltonrasc.ca</a>] On Behalf Of Al Jones<u></u><u></u></p>
</div><div><p class="MsoNormal">Sent: Saturday, May 12, 2012 6:00 AM<u></u><u></u></p></div><div><div><p class="MsoNormal">To: <a href="mailto:astronomers@hamiltonrasc.ca" target="_blank">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" target="_blank">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" target="_blank">astronomers-bounces@hamiltonrasc.ca</a><br>> [mailto:<a href="mailto:astronomers-bounces@hamiltonrasc.ca" target="_blank">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" target="_blank">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>> _______________________________________________<br>> astronomers mailing list<br>> <a href="mailto:astronomers@hamiltonrasc.ca" target="_blank">astronomers@hamiltonrasc.ca</a><br>
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