Lowell Observatory, in Flagstaff, Arizona is a fun place to visit, and loaded with history. Located on the top of the aptly named “Mars Hill,” this facility was the pride and joy of astronomer Percival Lowell. He is even buried there, right next to the Clark Telescope, which he used for many years in the mapping of so-called “canals” on the red planet, Mars.
The canals do not exist, but they were certainly very real in his active imagination, and he spent many cold nights observing the planet, and drawing what he thought he saw.
The telescope itself, is a fine piece of 19th century craftsmanship, and full of history. This may well be the most famous large telescope in the world, even if it’s known primarily for the now discredited notion of canal-building Martians. Other famous astronomers, including Clyde Tombaugh and Edwin Hubble used this scope at various times in their careers, as well.
Percival’s remains are located a short distance away in his own mausoleum, which features a beautiful stained glass ceiling. Just up the road from there is the so-called “Saturn Rotunda,” a round stone building that served as the observatory library. It has a domed roof, and features a Saturn-shaped chandelier inside the edifice. One can almost imagine Percival studying in this library next to it’s large fireplace on a snowy winter night. Inside the Rotunda, you will here the steady “click, click” of Clyde Tombaugh’s comparator; a machine used by Mr. Tombaugh in the discovery of Pluto. It is now located in the Rotunda Library.
Just around the corner from this historic building is the well-known “Pluto Telescope,” located in a small, circular stone edifice with an old wood gabled roof -that can open up to expose the telescope to the stars. I do not call it an “observatory dome,” because it was built in a “pre-dome” era. It is rather an “angled-cylinder” shape -built out of wood planking, and a smaller version of the huge wooden roof that sits atop the much larger Clark Telescope. The years have not been kind to this smaller roof, and it has a problem with leaking during rainstorms.
Under this roof, of course, is the telescope used by astronomer Clyde Tombaugh in his discovery of Pluto. What is surprising about this piece of history, is just how small it is. It was not optical firepower, after all, that led to the discovery of Pluto, but rather the ability to spot movement. Pluto, after all, moves against a fixed background of stars -when viewed on a succession of nights. Spotting this movement required the use of Tombaugh’s blink-comparator (the “clicking” device located in the Rotunda Library).
Two glass plate photographic negatives of the same patch of starry sky would be looked at through the comparator in rapid succession. The same background of stars were photographed on two different nights. When viewed in rapid succession in the comparator, the stars would appear unchanged. Pluto, however, being in orbit about our sun, would appear to move or jump when viewed in the comparator. In this way, Clyde Tombaugh’s keen eye was able to spot the movement of Pluto against the background stars.
As famous as this telescope is, however, it has fallen into disuse. It was built to handle Tombaugh’s glass plates, and doesn’t actually have an eyepiece to look through. Since astronomers no longer use glass plates, this telescope has become a relic of the past. It’s main purpose now is simply as a museum exhibit, visited daily by throngs of tourists.