This month is the telescope's 400th birthday. Well, sort of. We know that in September 1608 an optician called Hans Lipperhey announced that he had invented a new device and asked for a patent from the Dutch States-General. Before then it all gets a bit murkier. It's more than likely that someone (or some people) came up with a similar idea in the decades before, but Lipperhey was certainly one of the first to try and exploit the instrument's potential.

Portable telescope, dated 1661

The National Maritime Museum has a great collection of telescopes of all sorts (including this rather unusual trumpet-shaped one), so to mark the anniversary we've been putting together a display in the Royal Observatory, opening on 15 September, and a web exhibition. We're really trying to get over two points. Firstly, the invention was important because it was the first time someone had produced an instrument to extend one of the human senses. Thanks to the work of people like Galileo Galilei (who, incidentally, did not invent the telescope) it changed how people did science. Secondly, most of the telescopes ever made were actually for more mundane things than astronomy - for soldiers, sailors and pleasure-seekers, and not just astronomers. But don't worry, we're not forgetting that astronomical telescopes changed the way we think about the universe.

So come and have a look at the new display at the Royal Observatory - or the web version - and let us know what you think.