This telescope which uses large photographic plates, notice large cover with 2 handles on the back of the telescope,was used by Clyde Tombaugh in his discovery of Pluto. He would take exposures of the area of the universe where he expected to find the undiscovered 9th planet that could run as long as 45 minutes and he would have to make minor adjustments to keep the telescope perfectly aimed at the designated spot. These observations were made in the winter of 1930 and the observatory was unheated and open to the elements on this mountain peak and he would make several exposures per nite. By using a Zeiss Blink Comparator and his negatives he was able to prove the existance of our 9th planet Pluto and extrapolate it's orbit.
(sorry about the slight blurriness of the photo but this was a hand held exposure of over 2 seconds)