RASC Hamilton Transit of Venus

Ed Mizzi emizzi at cogeco.ca
Sat May 12 15:20:11 EDT 2012 

Thanks Roger, but how did you connect the coffee can to the eyepiece and keep it mounted properly? I cannot attend on that Sunday in May because I'll already be in Algonquin, but a great idea.

Ed


On 2012-05-12, at 1:04 PM, Roger Hill wrote:

> Ed...
> 
> I used a coffee can, with black construction paper taped inside to cut
> down internal reflections.
> 
> There are a number of variables you can play with to adjust the size of
> the image.
> 
> 1) The longer the distance from the eyepiece to the screen, the larger
> the image.
> 2) The shorter the focal length of the eyepiece used to project, the
> larger the image.
> 3) The longer the focal length of the telescope, the larger the image
> (think Barlow Lens).
> 
> Adjust the various parameters you can to give the best sized image.
> 
> 
> May I make a suggestion?  How about we gather at the observatory on the
> last Sunday afternoon in May before the transit and test out filters,
> projection systems, etc.? 
> 
> Get there for about 4pm and be set up for 6pm.  The Sun will be at
> (roughly) the same altitude and as the evening passes and the Sun sets
> you'll get a good feel for how the geometry of your equipment will
> change.  You may also be able to get some help with photography, too!
> 
> 
> Some of the people who will NOT be at Saltfleet (like myself) might be
> able to make the "dry run" and offer any assistance we can.
> 
> Just a thought.
> 
> Roger
> 
> 
> 
> -----Original Message-----
> From: astronomers-bounces at hamiltonrasc.ca
> [mailto:astronomers-bounces at hamiltonrasc.ca] On Behalf Of Ed Mizzi
> Sent: Saturday, May 12, 2012 12:34 PM
> To: astronomers at hamiltonrasc.ca
> Subject: Re: RASC Hamilton Transit of Venus
> 
> Roger, I am planning to do this as well. I received an 8" x8" piece of
> rear proj. material free (a sample from the manufacturer) but I'm having
> trouble finding the size of funnel used on that website??
> 
> Ed
> 
> 
> On 2012-05-12, at 12:26 PM, Roger Hill wrote:
> 
>> There's a great resource at
>> http://www.transitofvenus.org/june2012/eye-safety .  
>> 
>> You can find out how to make a "Sun-Funnel" at the above site, too.  I
> 
>> made something similar to view the 1970 March 7th solar eclipse, but 
>> since hi-performance rear projection screen material was not 
>> available, I sued a piece of wax paper, instead.  It worked quite
> well.
>> 
>> Roger
>> 
>> -----Original Message-----
>> From: astronomers-bounces at hamiltonrasc.ca
>> [mailto:astronomers-bounces at hamiltonrasc.ca] On Behalf Of Roger Hill
>> Sent: Saturday, May 12, 2012 12:08 PM
>> To: astronomers at hamiltonrasc.ca
>> Subject: Re: RASC Hamilton Transit of Venus
>> 
>> 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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