Sir Patrick Moore described Herschel as ‘the greatest telescope maker of his day’. The quality of the optics in Herschel’s telescopes, combined with his highly polished mirrors made from speculum metals, allowed the observer to see objects in deep space with remarkable clarity. Herschel supplied his seven-foot model to other astronomers and also sold parts for assembly. He went on to build ten-, twenty- and twenty-five-foot telescopes. All of these shared a similar design, utilising octagonal wooden tubes supported on a stand.
It is possible that Herschel may have begun work on his twenty-foot telescope whilst living in 19 New King Street (the home of the Herschel Museum of Astronomy), but it was not used until he moved to Observatory House in Slough. Although this was one of Herschel’s most accurate telescopes, his most famous was his enormous forty-foot model – the largest in existence for at least half a century.
Acclaimed at the time as ‘A Wonder of the World’ – Herschel’s forty-foot telescope even appeared on Ordnance Survey maps. Cumbersome to move, its huge mirrors often cracked or tarnished. The telescope was damaged in a gale in the mid-nineteenth century and was subsequently demolished. The museum has a scale model of Herschel’s forty-foot model (courtesy of National Museums Liverpool) and an early photograph of it taken by Sir John Herschel, which is framed with wood from the actual telescope. (The model of the 40 foot telescope is on display in the Reception Room, alongside the full-sized replica of Herschel’s seven-foot, reflecting telescope. The photograph can be seen in the Music Room of the Museum).
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