Do you recall the telescope below? It sits right inside the entrance to the Vatican Observatory’s offices at Castel Gandolfo in Italy. It was featured in a post from a few months ago about the Vatican Observatory and Our Lady of Good Counsel (click here for that post).
This telescope is one of the Observatory’s older instruments. It is the Merz refractor with “an equatorial mounting, an aperture of 10 cm and a focal length of 1.5 m” that “was located in the small dome on the half-tower near to the grotto of Lourdes in the Vatican” when the Observatory’s telescopes were located on the walls of the Vatican. It is also described in a 1908 article about the Vatican Observatory.
It is one sweet piece of old technology, especially its mount. Let’s take a close look at it. This is going to involve some jargon, O Readers, so if you don’t know your telescope parts you will just have to bear with me and figure it out as we go. It is not a long post!
Let us start at the bottom. Check out that sturdy pier! Notice the fine adjustment screws for turning the whole mount to point precisely north for polar alignment (below left, arrowed). There is a lot of travel in those screws. All you would have to do is have the mount’s polar axis pointing generally north and you will be able to get it adjusted exactly with those screws. Then note the levelling screws on the base of the pier (below right). There is a screw for adjusting the level of the pier, and then another for clamping that adjustment screw into place.
Then look at the latitude adjustment for the mount, to point the polar axis right at the north celestial pole. Note the teeth (dark blue arrow). There is an adjustment shaft (light blue arrow) that can be turned that engages those teeth and allows some better control in latitude than just muscling the mount into position. A knob of some sort would be fitted to that shaft.
Check out the main drive gears—in Right Ascension (celestial longitude), for tracking stars as the Earth turns by turning the RA axle. The worm gear that is the business part of the drive is indicated by the arrow. The other gears are for a clock mechanism or electric motor to drive the RA worm.
The Declination (celestial latitude) axle has gearing that is the equal of the RA axle. It also has a worm gear (arrowed—seen from two different angles below). This gearing is for fine adjustment in the north-south direction. For both the RA and Dec gearing, there would be knobs fitted that allowed the observer to make adjustments with ease.
This pier and mount were designed so that they could be set up and adjusted with precision, and then left to stay in place and remain as adjusted. This mounting certainly was built for the serious observer using a small telescope.
What about the telescope itself? Well it looks great with its wood tube and brass fittings. I did not try to test it out—maybe on another visit to the Observatory! But from the very small eye lenses both on the main eyepiece and on the finder scope, I bet it would be a little tough to use for a person whose observing experience is with modern eyepieces only. But if we could fit a modern eyepiece to this telescope I bet it would produce fine images. The 1908 article says that this “elegant” small telescope “although not of great potential, will be able to serve very well to observe the variation of the light of the stars and for similar work of astrophysics.” I suspect this would be a great telescope to observe with, at least once it was fully set up.
Like I said—maybe on another visit to the Observatory.