Eyes on the Sky - Francis Graham-Smith ***

There are broadly two types of popular science book - those that pretty well anyone would find interesting, and those where you have to be a bit of an enthusiast to enjoy it. Eyes on the Sky falls into the second category - there's nothing wrong with this, but it's just a rather different kind of book, one that concentrates on piling in the facts and not worrying too much about the narrative.

What we have here is an exploration of the uses of telescopes in astronomy, from Galileo through to some instruments that are still being built. The historical side is dealt with relatively quickly - we're on to the big telescopes of my youth by page 17 out of 230. The big era begins by inevitably highlighting what we always use to call in our ignorance the Mount Palomar telescope, but is now primly insistent in its old age on being the Hale 200 inch.

From there we go on to the bewildering array of modern telescopes, land and space based, covering every imaginable bit of the electromagnetic spectrum. (The book we written just too late to catch recent speculation that gravity waves might become the next generation of novel telescopy.) If, like me, you fall into the slightly nerdy second category, there are two aspects that are fascinating here - one is the sheer range of equipment out there. It's not just the big names like Hubble and Keck, but tens of telescopes you may never have heard of. The other bit that's even more interesting is finding out more about how these telescopes actually work. We're all pretty familiar with optical telescopes and radio telescopes (and good old Jodrell Bank, where the author worked, gets plenty of mentions), but may not be aware how an infra-red or X-ray telescope functions - yet these are now essential workhorses. With X-rays, and gamma rays for instance, you can't use a lens or a traditional mirror, and the methods employed are quite remarkable, especially the coded mask approach used, for example, in the Burst Alert Telescope that was mounted on the Swift satellite in use since 2005 (no, I hadn't heard of it, either). Used to spot gamma ray bursts, this looks like a vast jigsaw puzzle with about a quarter of the pieces missing.

Similarly interesting is the way that modern telescopes, particularly radio telescopes, often use a pair or an array of telescopes to either provide interference patterns or to simulate a vast telescope with a much wider reflector than could ever be built. I was aware of the concept, but the scale of something like the Square Kilometre Array is still remarkable.

Although the historical context was limited, it mostly seemed reasonable, though I'm not entirely sure of the statement that the telescope used by Penzias and Wilson to discover the cosmic microwave background radiation was built by Bell Labs to measure the radio brightness of the sky, as most sources suggest it was originally constructed for communications satellite/balloon experiments.

If you like to build your background knowledge and have an interest in how astronomy is undertaken, rather than just the results, this is the book for you. You probably won't consider this much of a holiday read, but if, like me, you have an interest in astronomy (and probably dabbled with small telescopes in your teens) it will be irresistible.

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Review by Brian Clegg