METEORS! — WHIPPLE 245 



meteor program at the Harvard College Observatory. This support 

 made possible the design and construction of special cameras. James 

 G. Baker designed the Super-Schmidt meteor camera (see pi. 2) 

 and the Perkin Elmer Corporation constructed six of these remark- 

 able instruments, two for the Naval Bureau of Ordnance, two for 

 the United States Air Force, and two for the Dominion Observatory 

 of Canada. Four of these cameras have been operated in New Mexico 

 for the past several years by the Harvard College Observatory, sup- 

 ported by the Office of Naval Research and the United States Air 

 Force, while the work of reducing the data has also been supported 

 by the United States Army, Office of Ordnance Research. 



The Baker Super-Schmidt camera has the unique optical design 

 shown in figure 4: the aperture is 12 1 / 4 inches and the focal length 

 only 8 inches, which gives the amazingly fast focal ratio of F/0.65. 

 The effective focal ratio, including the obstruction by the photo- 

 graphic film, is still F/0.85. Along with this remarkable speed the 

 instrument has a field diameter of some 55° without the rotating 

 shutter, reduced to 53° by the shutter, which is supported inside the 

 second glass shell and which revolves only about an eighth of an 

 inch away from the spherical surface of the film. The film itself con- 

 stituted a considerable problem because the emulsion has to rest on 

 a spherical surface with an accuracy of 0.0005 inch and with a radius 

 of curvature of only 8 inches. A process of molding photographic 

 film, suggested by the Eastman Kodak Co., has been developed at 

 Harvard, so that various types of blue-sensitive and panchromatic 

 emulsions can be satisfactorily heated and molded to this high curva- 

 ture without serious fogging or appreciable changes in the sensitivity 

 of the emulsion. 



Plate 3 shows an example of a meteor doubly photographed with 

 the Super-Schmidt meteor cameras at two stations. The breaks 

 in the trails were introduced by the shutter, which revolves at the 

 rate of 1,800 r. p. m. and cuts off the light for % of each shutter cycle. 

 During the open part of the cycle, which occurs each y 60 of a second, 

 a segment of the meteor trail is photographed. 



Without the shutter to reduce the over-all exposure time, on a moon- 

 less night in New Mexico we would be limited to only 2 to 3 minutes 

 instead of the 8 to 12 minutes which we can now use effectively. 

 Plate 4 shows a photograph of the Organ Mountains in the neigh- 

 borhood of Las Cruces, N. Mex., made with a 2-second exposure 

 at midnight, with full moon. The circle in the center of the photo- 

 graph is produced by the supporting hole for the rotating shutter 

 and not by the moon. 



Since 1952, some 6,000 meteors have been doubly photographed 

 by these cameras in New Mexico. The photographs provide a sur- 

 prisingly large quantity of information about meteoric phenomena 



