About our expert
The art of numbers
Under observation
Once CCTV was confined to the high street; now it’s invading your office. Discover who’s watching you work, and why.
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How star gazing can help to catch criminals
Dr Michael Hobson reveals how Crimewatch led his research in a new direction
"Have you ever wondered how astronomers produce those wonderful pictures that appear in the papers or on television from time to time? They certainly look very impressive, but in many cases it has taken a lot of work to turn the signal received by the telescope into a clear image of a star cluster or distant galaxy.
The basic images produced by telescopes often bear only a passing resemblance to the final pictures presented in the media or scientific journals. These `raw data' (as they are called) usually suffer from `blurring' and `noise' caused by the inevitable imperfections inherent in any measurement process. Therefore, an important part of modern astronomy is to develop ways of processing the raw data to remove these unwanted artefacts, and produce a clear picture, worthy of a slot on the Ten O'Clock News.
As an astronomer working in the Cavendish Astrophysics Group in Cambridge for the last 10 years, I have been very closely involved in developing a wide variety of `image reconstruction' techniques. These are basically mathematical algorithms that run on a (usually very large) computer. The program reads in the blurred, noisy data and attempts to reconstruct the actual image the telescope observed (which we generally call `the truth').
It is likely that I would still be working solely in the analysis of astronomical images if I hadn't sat down one evening with a cup of tea and happened across an episode of Crimewatch on television. In one particular item, a man had walked into a Post Office, threatened the cashier and made off with a considerable sum of money. Fortunately, the man has been caught on the CCTV camera. Unfortunately, as is often the case, the picture was terrible. It was so blurred that it was impossible to make out the man's features. Suddenly, I realised that the techniques I had developed for reconstructing astronomical images might work equally well at enhancing pictures like those taken by the CCTV camera.
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