view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Color photography of faint objects with a special fast film. Carpenter, E. F. ; Jepperson, Richard Abstract For some time Carpenter at the Steward Observatory and Duncan at the Mt. Wilson and Steward Observatories have been experimenting with color film as a simple, single-exposure, qualitative color-discriminant. Carpenter and Jepperson have recently obtained and tested some samples of an experimental Super Anscochrome film of encouraging speed and color characteristics. The emulsion is rated at ASA i6o without forced development. Since it is exceptionally red- sensitive, requiring a green-transmission filter for ordinary daylight use, the emulsion is not expected to become commercially available. With equal exposures the emulsion is found to be o.6 mag. faster than Super Anscochrome roll film, in keeping with the ASA ratings. At the ~6-inch Steward reflector an exposure of five minutes shows 13.8 mag. faintly, but well enough to distinguish between red and white stars. Reciprocity failure is considerable, a time-of-exposure factor of 3.6 being required for an extension of one magnitude. Color latitude is remarkable, red stars showing no appreciable dilution of color over an exposure range of 30 times, and only moderate dilution in a range of 6o times. Blue stars whiten much more rapidly with exposure time. The color latitude is much less with images of extended surfaces, since with these there is no possibility for the excess light to spread in the emulsion. We have as yet made no comparison of the registration of color as a function of stellar color index, but the gradient of the registration seems to be very steep, so that only the extremes of color can well be recognized, for example the distinction between red and white stars. The performance of the emulsion has been tested by photography of h Persei, XGC 1976 (M42), 1952 (Mi), and the following planetaries: NGC 65o (M76), 6720 (M57), 6853 (M27), 7662. The photographs of M I show most of the bright red filaments which appear in H~ photographs. The dominant red, green, and blue areas of the planetary nebulae are well differentiated. Some of the edges of M27 are red, while M57 has a bright red corona. M42 is particularly spectacular. The entire interior of the nebula is red, short exposures revealing an especially bright red edge to the central illumination southeast of the quadrilateral. On longer exposures the bright arms of the nebula which extend to the northwest and to the southeast are distinctly blue, and when the photograph is viewed with the north side upward these arms resemble a dark blue mantle draped over the red interior. There is surprisingly little spectral difference between the red and the blue areas of the nebula. With the sharp bright boundary between these areas placed across the slit, spectrograms of type F sensitivity appear identical except that the FNii~ lines XN6548 and 6584, as well as the ES"~ line X6726 are missing in the blue area of the nebula. But the color film is not sensitive as far out as X6726. Since H~ appears at normal strength in the blue area of the nebula, the tested emulsion is a very sensitive color discriminant. Steward Observatory, University of A rivona and Color Classics, Inc., Tucson, Aria. Publication: The Astronomical Journal Pub Date: March 1959 DOI: 10.1086/107859 Bibcode: 1959AJ.....64...49C full text sources ADS |