Wednesday 18 August 2010


Last week's post about sciencey stuff got me thinking more about astrophotography, and it's what I talked about on the radio today.

The first subject of astrophotography, unsurprisingly, was the Moon. Louis Daguerre had a bash at photographing it in 1839, but tracking errors meant his moon came out as a fuzzy spot. John Draper, an American doctor, chemist and scientific experimenter, made the first successful photograph of the moon a year later, a daguerreotype made over 20 minutes.

As new photographic processes were invented photography revolutionised astronomy, as celestial bodies that couldn't previously be discerned were captured. Check out Greg Allen's post on James Keeler's lantern slides of spiral nebulae, made in 1888, and Mark Graybill on how we slowly stopped thinking in terms of Milky Way = The Galaxy, and started thinking about about our local system being one of many.

Long exposure colour photographs of the night sky bring out elements we can't perceive, produced by light waves the colour sensors in our eyes aren't able to pick up. Something like the Hubble telescope is a different beast again. The telescope doesn’t use film at all; it records light from the universe with electronic sensors, in black and white. In another example, the Spitzer telescope captures infrared light, which is part of the spectrum we can’t even see. So the colourised images we do get to see have colour added during the processing stage. Basically, scientists map these images onto the blues, reds and greens that our eyes can perceive.

Many full-color Hubble images are combinations of three separate exposures — one each taken in red, green, and blue light. When mixed together, these three colors of light can simulate almost any color of light that is visible to human eyes. (This is how tvs and computer monitors recreate colour).

So, is it all trickery? I think not. The colour is added by scientists to help us understand the structure and subtle features of celestial bodies. There are open explanations of how this is done: in addition to Ray Villard's article on how colour is used in astrophotography, which I linked to last week, and Robert Hunt (the Spitzer's Visualisation Scientist) on the same topic, the Hubble website has a great section explaining how colour is used in Hubble telescope photographs.

A side effect, of course, is that images are produced that we seem to beautiful, even magnificent (see the Guardian's art critic Jonathan Jones on this topic). The closest I've ever come to a religious feeling was when I read about cosmic rays - muons that come from outer space, pass through the earth's atmosphere, and down into the Earth. I suddenly felt like something much bigger than myself. Particles that had come from the sun could be passing through me right now. (I know, woo-woohhh). But astrophotography seems to bring forth that same sense of wonder that, in these jaded times, it's pretty hard to find.

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