Probably the best example of this type of mounting applied to a refractor is that made by the elder Cooke of York for Fletcher of Tarnbank; the polar axis is of cast iron and the mounting very satisfactory and convenient, but unfortunately no detailed description has been published.
Fraunhofer's chef-d'oeuvre, the great Dorpat refractor, made for Otto Struve about 1820, had a mounting of this type, and was the first equatorial of any importance to be provided with clockwork.
The largest example of his work is the refractor of 24-in.
This was first accomplished by Grubb in the great refractor of 27-in.
For the great refractor more recently erected at Potsdam, Messrs Repsold arranged a large platform mounted on a framework which is moved in azimuth by the dome, so that the observer on the platform is always opposite the dome-opening.