A Special Moonwatch Feature by One who was There

The Transit Scopes of the Moonwatch Program

Anna Hillier

I have been asked, “Why did people look down instead of up?” The question concerns the Moonwatch scopes used to track the first space satellites, beginning with Sputnik 1 in October 1957.

These scopes were called transit scopes because they were designed to see a wide field of view and to watch for objects that pass in front of (transit) the eyepiece. They were designed for the express purpose of the Moonwatch program and were never meant for nightly observing sessions.

The rules that were established by the organizational committee at the Moonwatch conference were simple.

One could buy the parts from an optical supplier and build you own scope using the design provided in the Bulletin for Visual Observers of Satellites.

Or one could order the Edscope already constructed for $20.00. This design looked like a finder scope pointing down at the flat instead of an eyepiece.

The scopes consisted of a flat or front surface mirror at a 45-degree angle permitting the sky to be reflected into an eyepiece. The eyepiece was an Erfle with a 1.25-inch focal length and a 68-degree field of view, providing a wide area of the sky to watch. The eyepiece was set at eye level, so no matter what setting was applied to the scope the observer had a comfortable position for observing. This was important, for sessions could last as long as an hour.

Figure 1. Plan of Win Shattuck's Moonwatch transit scope in upper position for overhead satellite overpasses. Courtesy of Anna Hillier.		Figure 2. Plan of Win Shattuck's Moonwatch transit scope in lower position. Courtesy of Anna Hillier.

Observation reports were sent to Moonwatch Central, the main reporting room at Harvard College Observatory in Cambridge, Massachusetts. This was where organizational meetings for tracking the US Vanguard satellite program were held. Station network reporting was done via Teletype or Western Union. The telephone was used when faster communication was necessary.

The observing station was placed on the roof of the Harvard College Observatory, where the Amateur Telescope Makers of Boston had their observational training programs and where the actual observations were recorded and tracked.

The Amateur Telescope Makers of Boston were asked to design a transit scope that would be used for Moonwatch. Win Shattuck designed a scope that was perfect for the job. Sam Gardiner worked with the optics. Twelve scopes were finished ahead of schedule, which meant they were ready when the Russians put the first satellite into space ahead of the US Vanguard program.

Other Moonwatch teams were organized into a worldwide network and used their versions of transit telescopes for their observations. When the scopes were no longer used, they were retained by the owner or returned to their point of origin.

There is much more information about Moonwatch on the web, including at NASA and various International Geophysical Year and International Heliophysical Year sites. The October 2007 issue of Sky and Telescope has more. Memories will be shared at the Remembering the Space Age conference in Washington, D.C., on 22-23 October 2007 at the American Association for the Advancement of Science (AAAS) Auditorium.