The comments have proved to my satisfaction that the effect noted here is an artifact of the lens and not a crescent of Venus. So the discussion here is faulty.
Thanks to the person who put up the comment. The issue is that there are simply too many pixels in Venus...
However I am left perplexed as to why Venus pixelated as a crescent - with the lit side tilted towards the sun (as you would expect) and Jupiter and the Moon look like circles (the moon) or squares (Jupiter). If someone is able to give a good optical explanation I would appreciate it.
Meanwhile I will try to replicate the Brad Delong picture with a mobile phone camera and a 10 megapixel SLR.
Brad Delong has a photo on his blog taken with an iphone of the moon, Jupiter and Venus.
It is impressive – and through it – looking at the individual pixels – you can tell that Venus is a crescent.
Now all Galileo did – which marks him as one of the greatest minds of all time – was look at Jupiter through a simple telescope and plot the four moons (I have never been able to resolve more than four moons). And if you do this regularly – certainly every evening for two or three weeks – you will come to the conclusion that the moons circle Jupiter. Galileo’s letter to the Prince of Venice is here and an English translation of the text attached to the diagrams is here.
Galileo did not distinguish between the moons and stars – the notion that the sun was just another star far out in the uncharted backwaters fo the unfashionable western spiral arm of the galaxy was beyond him. But he did work out that the “Medici Stars” revolved around Jupiter and that was a major challenge to the authorities.
The second great Galileo experiment was to work out that Venus revolved around the sun – and for that he took observations in the morning and the evening for considerable time – observing the crescent shapes.
And Brad Delong has shown you can do that with an iphone.
Here is Brad’s image
– and here is an expansion of the pixels of Venus.
When technology that good is easily available the excuses for basic scientific ignorance are becoming thinner and thinner.
Now to take the eight year old out with an iphone and teach him some real science! There are few excuses...