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The links between Canterbury and the great telescope makers of the past may not be obvious…

Around 1520 in Bareham, near Canterbury a little known British scientist and astronomer Leonard Digges was born. In 1553, he wrote a series of books detailing his theories and observations. These included rules and tables for astronomy; tables of the Moon's motion; a description of how to tell the time during day or night; descriptions of meteorological phenomena and an account of their causes. The book also had a short description of the Universe according to the system of Ptolemy with tables of the dimensions of the planets and their orbits. He was credited by his son (Thomas) with inventing the telescope. Although there were many claimants to this title 30 years or so later, none appears to be original, and some point to a source of inspiration in Britain.

Herschel's 40 foot telescope

It is possible that this source was Leonard Digges ‘perspective glasses’ as he called them. Digges was rightly credited with the invention of the theodolite and some see his early work and that of his son as a credible claim for the first telescope. Digges claimed to be able to see the movement of troops at a distance of 7 miles using his device. There were of course many great telescope makers in British history, Isaac Newton in the late 17th century created a design of reflecting telescope that is used to this day. The pre-eminent telescope maker of the late 18th century however must have been William Herschel who made his own telescopes in Bath and then Slough (see Peter's article on Uranus ).

The third Earl of Rosse's Leviathon

Herschel’s 40-foot telescope was the largest in the world at that time with a 40˝” mirror and a 40-foot focal length. His telescope was unrivalled in size until the emergence of the Leviathon in 1845.

The 28inch refractor at the RGO, Greenwich

The third Earl of Rosse in Birr, Ireland called upon his neighbour (Thomas Grubb) to design him a new larger telescope 6 foot in diameter with a 53-foot focal length, the locals called it ‘the Parsonstown Leviathon’. The Earl, William Parsons, was an accomplished telescope builder in his own right, however this partnership was to be cemented later. Thomas Grubb manufactured telescopes in Dublin for observatories around the world; his business was taken on by his youngest son Howard Grubb. Sir Howard Grubb built the 28” refractor for the Royal Observatory Greenwich, which is still the largest refractor in the UK. Unfortunately, after 95 years of making telescopes, Grubb went into liquidation, but were bought out by Sir Charles Parsons (the son of the third Earl of Rosse) who retained Sir Howard Grubb as advisor, and in 1925 moved the combined company to Newcastle. Grubb Parsons produced some 50 telescopes mostly for large observatories, but by 1985 the company was again struggling, and lasted only long enough to deliver the 4.2m William Herschel telescope (the WHT) that was sited on La Palma in 1985. The company then went into liquidation. While the delivery of the WHT was a fitting epitaph and their largest telescope ever, it was a sad day for British Astronomy.

Graham, Bob and Noel under the WHT in 2008

However, in their more prosperous period in 1967 the Royal Observatory Edinburgh commissioned Grubb Parsons to build a 50cm training telescope for use by the University to train students on the use of instrumentation. The University of Glasgow commissioned a similar scope for the same reasons a year later. While the use of the telescope has been a great success for the University of Edinburgh (who now are global specialists in telescope instrumentation design), the scope itself is no longer used. The ROE in concert with the STFC have therefore asked if any amateur societies would like to take it on..... Your society with its links to the earliest telescope makers in Canterbury would of course love to be able to install this iconic and valuable instrument in our observatory . We have therefore applied to the ROE to be considered for owning the telescope, once it is decomissioned.
We intend to use it to assist in hunting asteroids (see Ian’s article on the hunt for 2005 YU55 in November ). Many of us would like to view the stars through such a magnificent telescope as well! We expect it to have a very flat field of focus, which means it will be ideally suited to imaging. In addition, being a reflector, it should be completely free from chromatic aberation, making it suitable for detailed spectrographic analysis. We will be hoping that once Bob has perfected the design of his own spectrograph , that we can commission another from him! An instrument of this diameter should allow us to engage in minor planet observation; to date Peter is the only member to report viewing these (see Peter’s report on Vesta ).

Ian recently took an interest in Asteroid occultations here is an amazing picture of Antiope A & B based on occultation timings produced with amateur observation reports.

The ROE's 20 inch Grubb Parsons Scope

Ian’s pictures of the super nova in M51 last year (SN2011dh ) were an interesting glimpse of a Supernova. However, a larger telescope would allow fainter galaxies to be monitored (with the just a possibility that we might actually detect one). In addition, for nearer outbursts we may actually be able to produce a spectrum from it. However, the missing data regarding these dramatic events is the routine patrol and follow up monitoring of the decaying light curve. This is something that a scope of this size is well suited for.

We have no way of knowing (at this stage) how the ROE will view our application, but we can't help but dream, and some of our members have some very big ideas for this scope!

Article by Noel Clark, 2012
References to other articles are on our old website, and therefore no longer available.


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