A Test of the Abundance of the Heavy Isotope of Carbon in a Graphite Meteorite

These values are plotted in Figure 1. Dots indicate magnitudes derived from the 4-inch camera plates. Open circles represent the magnitudes obtained with the 18-inch Schmidt telescope. This instrument has a focal ratio 1:2. Under the best conditions it reaches a limiting magnitude m = 17 with an exposure time of ten minutes on ordinary non-color-sensitive portrait films. For the use of the 18-inch Schmidt telescope and a grant of funds for its operation we are greatly indebted to the Observatory Council of the California Institute of Technology.