The Damon Telescopes

One of the biggest contributions of Edward Pickering, who was the director of Harvard College Observatory for 42 years (1876-1918), is initiating a program to map the variability of objects in the night sky [1]. One of the main consequences of this program was to collect a huge number of high quality plates that will form a Sky Atlas of an accuracy of +0.3 to +0.5 magnitudes. The first plate in this program was taken in 1893 with a 63.5mm (2.5 in) Ross Portrait objective [2], all the following plates were taken using patrol telescopes to form the AC, AI and AM series. These plates were later used by so many scientists from all over the world discovering new comets and quasars in the sky.

Later, after Donald H. Menzel stopped the Sky Patrol program in 1953, he decided to restore it. Thus, he began to develop the Damon cameras to create a three color atlas of the sky in February 1960, until they were used in 1968 [2]. These cameras were named after their main contributor Ralph S. Damon [2]. This program is also required to cover the northern and southern hemispheres, but with more improved cameras that work in threes. These cameras were unique of capturing the same image in the blue, yellow, and red direct images.

Fig(1): the cross section of the Damon camera

          The Damon cameras were designed to cover a field of 31⁰ x 39⁰ per plate, have an exposure time of two hours, easy to operate, independent from the two other cameras, and  have a shelter that endures diverse weather conditions. They are operated by a synchronous motor and a gearbox. A cross section of the camera is shown in figure (1) above. These cameras are controlled by an electronic control console having the power supply for the motors, power distribution unit, tuning fork oscillator, and a driving unit for the synchronous motors. Also their shields were designed in a specific way to be mobile and not attached to the ground. Thus, it was made of detachable housing made of polyester resin reinforced with fiberglass as shown in figure (2) below.

Fig(2): removal of the shelter of the Damon camera

These new cameras have a lot of advantages that helped in discovering  a new era of the sky patrol. Some of these advantages are that the plates were sharp to their edges without vignetting problems, helpful in analyzing heavenly bodies as quasars, identifying novae to a fainter limit, and discovering comets at the times of sunset and sunrise. These plates covered the whole sky from -90⁰ to +90⁰ with an overlap of 2⁰ to 4⁰. Therefore, these plates were not for general use but they were preserved for the purpose of the sky atlas.

 

 

References:

[1]        Bitterman, Jay. “Astronomy Biography of Edward Pickering.” The Lake County Astronomical Society. Lake County, Illinois, 21 May 2012. Web. 15 Aug. 2014.

[2]        Ingrao, Hector. Menzel, Donald. “New Sky Patrol Program at Harvard College Observatory.”