Visions of Venus

The great transit was best seen with a reversed scope projecting sunspots and the outline of Venus onto a white card a short distance away.  The first sighting (positioned at about 10 oclock on the sun’s rim below) at about 6:11 pm EST on Tuesday June 5 was exciting:















The best pinhead mirror image just showed Venus and streaks of cloud but no sunspots. 

  The pinhead mirror resolution was improved by Scott’s addition of a punched hole in a card in the beam from the sun just in front of the mirror.

 I masked off the mirror with tape, leaving just a small triangular corner exposed to get a similar effect. 


John asked if diffraction, or scattering of sunlight as through gaps in tree leaves, was simply bending the light to give the image Lomonosov saw centuries ago?  L. took it to be an atmosphere for Venus.  I don’t think the light is bent that much. I think the images of light through leaves are simply umbra and penumbra shadows mixed with poor resolution pinhole images; Catalpa tree leaves do this well – see typical image below:


We did not see the rim of light which Lomonosov  saw about 250 years ago, which was genuine scattering from Venus’ CO2 atmosphere. This is what that looks like with a big telescope:

 Diffusion scattering happens on a very fine scale when sunlight hits a single spider web filament, or very fine scratches on glass. Such thin lines act like an optical grating or prism and create rainbow colors. Very hard to photograph but you can see it in these two Photoshop enhanced cell-phone images of sun and glass scratches. (I only increased the saturation and did not add any colors that were not there originally)


Diffusion is what makes waves bend around solid objects. It’s easy to see with water waves. But individual particular photons also act like waves and do bend a little around a sharp edge.  Even actual atomic particles, some as big as 70 atom Buckyballs can also show their wave-like propety and diffuse a little as they pass by an edge. It gets even stranger: human size aglomerations of carbon, hydrogen and other atoms – you and me – also diffuse very slightly when we pass close to the edge of a narrow doorway without actually touching it. The diffusion is too small an amount to be measured but it can be readily calculated. I think we get smeared by about 10E-50 meters or so. I can’t find the exact amount right now but it is somewhere in my scattered library.

Safely See the Sun

Next June 5 (Tuesday), until sunset in North America and June 6 in Ireland after sunrise, you can see Venus cross in front of the sun. She only does this twice every 113 years.I have some small pieces of very flat (6 mm float glass) front surface reflectors to give away. The diagrams below show to easily set up the “Pinhead Projector” I developed 18 years ago when Toledo had an annular eclipse.  Keith used it successfully the other day in Osaka. (see his blog listed above).


In practice I set a 25 mm (1 inch) square of mirror in Plasticene and adjust it to reflect a sun spot deep into a dark room. When set up, I then put a washer over the mirror to reduce the aperture.  The smaller the hole, the shaper the image but it also becomes less bright and so needs a darker room. Below shows Hermes watching the distant image, and wondering, with the washer/mirror/Plasticene (green) pinhead projector in the bottom of the picture.

The photo at the top of the blog is a quick, coarse shot showing tree branches half covering the sun. It’s fun to watch them move in the wind, and it’s a good test of the system.

When I tuned the setup by masking the mirror with a 5 mm (5/16″) dia opening I got the sharper 100 mm (4 inch) dia image below of leaf and  branch in front of the sun, on the wall of a dark room, 13 m (40 ft) away from the pinhead projector, with no window and the door just opened enough to admit the beam of light.



Physics Today tells the story how in 1760 Mikhail Lomonosov was the first to ever observe that Venus has an atmosphere:

I don’t expect myPinhead Projector to have enough resolution to show that aureole, but it did project a great 400 mm dia annular solar eclipse image on the far wall of an empty, dark warehouse many years ago when I first tried it.

I have a few pieces of the flat front surface (80% reflection) to give away. Tell me very briefly why you’d like a small piece of the mirror and I’ll try to get one to you (while supplies last) in time for Venus Transit.

There is a good website on the topic at