Palomar History Photo of the Week - Building the Horseshoe

On January 17, 1939, seventy two years ago today, the last of the three big pieces of the 200-inch telescope's north horseshoe bearing was lifted into place. The bearing is a key component the 530-ton telescope, allowing it to pivot to look east or west. The horseshoe bearing floats on a thin film of pressurized oil and helps to support the weight of the telescope.

These photos were taken from the dome's inside catwalk by Lee A. Farnsworth, Jr. who worked at the observatory during construction of The Big Eye.

The first picture captured the view from just southwest of the telescope looking northeast toward the horseshoe. The east horn of the horseshoe is easily visible on the right.


The second photo shows the west horn of the horseshoe as it is being lifted by the crane at the top of the dome. The


The final shot shows the west horn of the horseshoe being lifted into position. Note the person in the photo. The fully assembled bearing is 46 feet across would still need to have its pieces welded together to become functional.

The successful welding of the horseshoe marked the completion of the telescope's mounting structure. In the months that followed the Palomar crew would move on to assemble the 200-inch telescope.