The Baker super-Schmidt meteor cameras.

The first super-Schmidt meteor camera, designed by Dr. James G. Baker, manufactured by the Perkin-Elmer Corporation and purchased by the U. S. Naval Bureau of Ordnance, was tested at Norwalk, Connecticut in late May. The camera was flown to New Mexico where it is now installed and in operation at the Soledad Station of the New Mexico meteor-observing stations, approximately 12 miles east of Las Cruces, New Mexico. The camera has a numerical aperture inches, focal length 8 inches, optical focal ratio F/o.65 and effective focal ratio F/o.82. Its field is ~~0 with almost no vignetting. The rotating shutter covers 520. The preliminary tests showed that the image quality is excellent over an area of diameter 400, the diameters of the photographic images of faint objects being of the order of 25-30 microns. At the edge of the field, some 27210 from the optical axis, the image quality is still reasonably good, the diameters becoming approximately twice those nearer the center of the field. More than 8o per cent of the light is concentrated within these measured diameters. A rotating shutter is mounted inside the correcting shell, approximately 2 mm from the surface of the film, reducing the total field diameter to 520 for meteor photography. Since it is difficult to hold the film accurately to the surface of the film holder in the outer 6 inch of the radius, no effective loss is introduced by this restriction on shutter dimensions. The shutter occults at intervals of 1/3600 second and is open one quarter of the time. The effective exposure times on a clear moonless sky with a rotating shutter will be approximately 15 minutes on films selected for maximum sensitivity at exposure times of the order of 1/1000 of a second. Because of the sensitivity of image quality to focus, the system is quite sensitive to temperature changes. The best solution appears to be a thermostatic temperature control of the entire camera. From preliminary tests made in June 1951, the limiting visual magnitudes photographed are, roughly, for slow meteors >4, for average meteors 3-4, and for very fast meteors 2-3. The work was performed under a U. S. Naval Bureau of Ordnance contract. Harvard College Observatory, Cambridge, Mass.