Tag Archives: telescope

Visions of Venus

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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:

 

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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.

Spring Arrivals

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Two weeks ago (April 23) we had the first batch of ducklings two of goslings, and a new moon. The goslings run under mother’s wings when the hawk is near. And the bees have doubled their accommodations The new moon had bright Venus (not in the picture below) close by.  It’s fun to look at the sky and think where we are in the solar system in three dimensional terms. When the Sun is down it is really only behind the Earth. Look at the moon and it will “Point at the Sun”.

Venus too can be seen in her varying positions in the Western evening sky or the Eastern early morning sky. With a little telescope you can see a large thin bright crescent when she is close to us, or when on the other side of the sun she appears to be very small (about 1/3 the size when close) and full ; when she is the highest in the evening sky, she is at the same distance from us as the sun is from us, she looks like a 1/4 moon, half in shadow, and of intermediate size. I am still trying to decide which of the 3 is the brightest? Another way of sensing our place in the dynamic solar system is to watch a sunset and think not of the sun setting but of Earth rapidly rotating with the sun stationary and our horizon rising up in front of the sun (don’t fall over backwards).