Professor Tom Ray of DIAS – an expert in Astronomy – said: “Grubb’s work was of such high quality that much of the equipment the firm built is still in use today. A fine example of his work can be seen in Dunsink Observatory, part of the Dublin Institute for Advanced Studies. This telescope, known as the South Refractor, is still used by the public to view the stars and planets. Despite being 150 years old, its Victorian clock mechanism and mechanics function perfectly.“The instruments developed by the Grubb firm were critical in proving Einstein’s Theory of Gravity and revealing the presence of Dark Matter. A Grubb lens and coelostat – a device for feeding the lens with a stationary image of the sun – were used in the 1919 eclipse expedition that tested Einstein’s Theory; and were fundamental in proving Einstein correct. Both devices are now in the possession of DIAS.“The 19th Century was a time of huge innovation and excitement in astronomy, and Ireland played a key role. It is fitting, therefore, that a permanent marker has now been erected to commemorate Thomas Grubb, Ireland’s telescope-maker extraordinaire.”