Check out this telescope. It is a Newtonian reflector, meaning it uses a curved mirror at the base of its tube to reflect an image up to an eyepiece mounted on the side of the tube. It rides on an Altitude-Azimuth mount (meaning the mount has up-down & left-right motions). In that regard, this telescope is much like a common “Dobsonian” design used today with large, relatively low-cost telescopes.
But this telescope is no Dobsonian. This telescope was not made to be low-cost. It is a work of art. It is a telescope that is also a piece of fine wood furniture. Moreover, it is equipped with some pretty cool “old school” technology that allows its user to focus and precisely steer the telescope, with all controls handy at the eyepiece. In the picture below you can see the focus control knob (yellow arrow), the altitude control knob (green arrow), and the azimuth control knob (blue arrow).
The pictures below are of the focus control. The telescope’s eyepiece is mounted on a brass plate, which is moved back and forth by means of a knob and threaded screw (arrowed). I could not see inside the telescope, but I presume the secondary mirror that deflects the light toward the eyepiece must also be attached to that plate, with the whole assembly moving back and forth to focus.
The altitude control consists of a sort of “rack and pinion” device as seen below — a crank on a curved, toothed metal bar. Turn the crank one way and the telescope moves upward in altitude; reverse the cranking and the telescope moves downward. The toothed bar is attached into the base of the telescope’s mount (arrow).
Perhaps the most remarkable thing about the telescope is its azimuth control. The azimuth control knob seen earlier is connected to a shaft (below left, yellow arrow), which connects to gears that turn a large pulley (blue arrow in both pictures below). That large pulley drove a belt, now absent, that was guided through two guide pulleys (below right, red) and that went around a second large pulley (green).
The second pulley (green again, below left) was attached to a screw (orange), which engaged with teeth to turn the telescope mount, which rode on wheels (below right), in azimuth. Note that the wheel has a very limited distance it can travel. Whereas the altitude control crank could move the telescope through large changes, the azimuth control knob was very limited in range. Presumably large changes in azimuth were made by rotating the entire mount.
As cool as the azimuth control mechanism is, I suspect that it did not work that well. The long chain of shafts, gears, pulleys, belt, and screw looks as if it would be prone to having a lot of free play, making it frustrating to use. But maybe not — it is all quite finely crafted, after all.
Where is this telescope? At the La Specola Museum in Florence, Italy. The photo below shows the view out one of the windows of the tower in which the telescope is located. I got to see this telescope in 2017, with a group of folks on a Vatican Observatory tour. It is one very cool instrument.
