The invention that revolutionised amateur astronomy

John Wall
Image caption Engineer and inventor John Wall, inventor of the Crayford Focuser

Stargazing Live is back and as part of the Brian Cox-based excitement we're looking at one of the unsung heroes of amateur astronomy - an inventor who revolutionised telescope design.

In 1971 engineer John Wall, who now lives in Coventry, published a paper in the Journal of the British Astronomical Association. You can read his original paper complete with hand drawn diagrams here.

In those days actually building your telescope was a big part of being an astronomer and John Wall realised the traditional approach to focusing the telescope wasn't good enough.

At the time the eye piece used a rack and pinion mechanism which was clunky, expensive and tricky to make. John did away with all that and created a simpler mechanism using a metal tube pressing against four rollers.

He sketched the idea and built the prototype in two days. In a sign of good design the prototype worked first time. Very unusual in engineering.

Crayford Focuser

He named it after the town he lived in and the astronomy society he was a member of and so the Crayford Focuser was born.

John quickly realised his idea was being adopted by amateur astronomers all over the world. When mass manufactured hobby telescopes arrived they too would use John's idea. John told me he thinks "millions of them" will be made in China this year.

But John didn't patent the Crayford Focuser, instead he gave it away for free. His reward he says is seeing it so widely adopted all over the world. And perhaps he does enjoy a little bit of celebrity for those in the know at the Coventry and Warwickshire Astronomy Society where he is now a member.

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