RASC Hamilton Transit of Venus

Sat May 12 12:05:17 EDT 2012

The event won't start in our area until just after 6pm.  

There is a very safe way to view the event by using the equivalent of a
pin-hole camera.  Completely darken the room, but let a small (try 1/4
to maybe 1/2") circular spot of sunlight fall onto a mirror, and then
bounce that onto a screen.  Make sure that the screen is at least 100x
further away from the hole than the the diameter of it.  So...a 1" hole
should be projected onto a screen at least 100" away.  

This "trick" has been used all over the world to show students the
progress of a solar eclipse.  

I see no reason why it shouldn't work with Venus, although I have never
actually tried it.  I've always been outside with a safe filter!
However, if you've ever seen pictures of crescents of light formed by
ad-hoc pinhole cameras (the gaps between tree leaves, for instance),
it's the same effect.  What could be a great picture, might be
photographing the dappled light under a tree, each of the circular
dapples having a black spot on it! 

If you're going to project, then it might be best to use a Barlow lens
rather than an eyepiece, and that way the Suns rays never come to a
sharp point.  The (cheap) barlow won't get as hot as an eyepiece, and
should do a reasonable job.

And I see no reason why a pair of 2x2 #14 welders glass securely (and I
cannot emphasize that enough) attached to the front of a pair of
binoculars should not do a good job.  Put them on a tripod though...it's
tough to find the sun, and you can't look to see if you're in the right
area of the sky.  On a tripod you can look at the shadow and minimize
it...then you know you're in the right area.

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 10:36 AM
To: astronomers at hamiltonrasc.ca
Subject: Re: RASC Hamilton Transit of Venus

Will, I'm going to take a look on the WWW to search for solar projector
screens

Ed

On 2012-05-12, at 10:33 AM, will gray wrote:

> Hi Ed and Jeff,
>  
> I am in the same boat as well,  there will be a bunch of students at
my highschool who will be very interested in seeing the transit and I
think the best way to view it is by using my 80 mm referactor with a
projection screen..... I feel safer and happier about doing this than
handing out  25 pairs of goggles and having some potential
mishaps....but I've never done it before and want to make sure I do it
safely and properly.  Any thoughts would be much appreciated as well.
>  
> Will
>  
> > From: emizzi at cogeco.ca
> > Date: Sat, 12 May 2012 10:29:01 -0400
> > To: astronomers at hamiltonrasc.ca
> > Subject: Re: RASC Hamilton Transit of Venus
> > 
> > Jeff, I want to use a solar projection screen with a group of young
students. Do you have ideas about how to set that up. I was hoping to
use both a pair of binoculars and an 8" Dob?
> > 
> > Ed
> > 
> > 
> > On 2012-05-12, at 6:47 AM, Jeffrey Coe wrote:
> > 
> > > Hi RASCals,
> > > 
> > > Not to forget: the use of a solar projection screen.
> > > 
> > > Jeff
> > > ----- Original Message -----
> > > From: "Al Jones" <althemanjones at gmail.com>
> > > To: <astronomers at hamiltonrasc.ca>
> > > Sent: Saturday, May 12, 2012 6:00 AM
> > > 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
> > >>> _______________________________________________
> > >>> astronomers mailing list
> > >>> astronomers at hamiltonrasc.ca
> > >>> http://hamiltonrasc.ca/mailman/listinfo/astronomers_hamiltonrasc
> > >>> .ca
> > >>> 
> > >>> _______________________________________________
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> > >> 
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> > > 
> > > 
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> > 
> > 
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