300 AKmjAL REPORT SMITHSONIAN INSTITUTION, 1961 



which an electron beam pulses on and off in synchronism with the 

 time. This beam is presented on an oscilloscope somewhat similar 

 to the picture tube in a television set. The clock with the oscil- 

 loscope and the electronic sweep was installed in the dome of the 

 15-inch telescope at the Harvard Obsen^atory, and the following 

 weeks were spent developing a usable system of time presentation 

 on the oscilloscope. 



The next step was to find a radio receiver that would give reliable, 

 consistent reception of the WWV time signals from Beltsville, Md. 

 Davis chose a fixed-frequency receiver so that station personnel could 

 not use the set for listening to anything except WWV ! 



It was then necessary to arrange for some emergency power supply, 

 since the stations would be located in areas where the local power 

 would not be especially reliable. Following specifications drawn up 

 by Davis, an electrical firm in Cambridge built an emergency system 

 similar to that used for railroad signals. It worked exactly as 

 required but used a rather expensive type of battery. Since the cost 

 was prohibitive, the 12 camera stations were actually supplied with 

 emergency power systems using ordinary automotive batteries, which 

 were to prove inadequate. 



By the end of June 1956 the timing system pieced together from 

 various components was functioning satisfactorily at the Harvard 

 Observatory. The staff then began to think seriously of how the 

 time presentation could be photographed inside the Baker-Nunn 

 camera. Dr. Hynek obtained from Edward Halbach of the Mil- 

 waukee Astronomical Society a photographic slave clock that was 

 compatible with the modified Norrman Time Standard and that 

 illimiinated whirling dials by means of an electronic photographic 

 strobe lamp. After preliminary testing, Hynek and Davis deter- 

 mined that this slave clock was essentially what they would need, 

 once an oscilloscope presentation was added to it. Now they had 

 a complete prototype slave clock that, properly reduced in size and 

 made to fit mechanically inside the Baker-Nunn camera, would give 

 the time presentation required. 



In July Mr. Norrman came to Cambridge and was shown the 

 assembly. This led to his building the model 111, which was bas- 

 ically a model 110 with the oscilloscope, the auxiliary circuits for an 

 electronic presentation of microtime, and other accretions. Mean- 

 while, Davis completed the assembly of a prototype time station and 

 successfully tested it in August. 



Davis then went to California to discuss with Joseph Nunn and 

 with Boiler & Chivens the integration of the clock and the camera. 

 A firm decision was made that all the synchronous motors in the 

 camera would be driven from the accurate 60-cycle current of the 



