Uranus in 2003

6 Sep 2003

Uranus; 6 Sep 2003, 23:53BST (22:53UT). My first attempt to photograph Uranus. Even ignoring the spurious colour (yellow to the top, blue to the bottom) caused by the low altitude and less than perfect optics, the overall blueish green colour of Uranus is evident. The extreme distance of Uranus from the Sun means it has a relatively low surface brightness, creating a challenge for the webcam to capture it. Turning up the gain created a certain amount of background "noise" in the image - although successfully removed by reducing the brightness of the image after processing, it means that I do not entirely trust as genuine the apparent detail visible. Philips ToUCam Pro, Barlow projection on 8.75inch f/7.3 Newtonian telescope. 1/25s @ f/17. Scale of 0.15 arc second (= 1800km) per pixel. 232 frames stacked with Registax v1.1.

This picture was taken just a week after Mars' close approach to the Earth, with Mars not far from Uranus in the sky, but at very different distances. Although Uranus is over 7 times the size of Mars (52,000 vs. 6,800 km) it appears far smaller in the sky (just 3.8 arc seconds compared to Mars' 24) owing to it being massively further away (2,700 vs 57 million km). Compare the apparent size Uranus above with Mars taken on the same night. Both pictures are at the same magnification - twice the original as created by the webcam.

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