Wednesday 8 November 2023

The Thomas Cooke 25 inch lens tested

On November 5th 1867 the 25 inch object glass which had been so long in the making by Thomas Cooke of York was completed. This was the largest object glass to that date. 

 It was tested on the double star gamma 2 Andromeda and the stars were seen most distinctly divided and with the spurious disks of the three stars of the system perfectly round.

When completed in 1870 the telescope would be used by Robert Newall in Gateshead, at this time it was the largest telescope in the world.


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