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The S201 far-ultraviolet imaging survey. II - A field in Cygnus
Far-ultraviolet imagery of a region in Cygnus, a 20 deg diameter fieldcentered near (1950) R. A. 21 h 31.2 m decl. +37 deg 25 arcmin, wasobtained by the S201 far-ultraviolet camera during the Apollo 16mission. In a 10 minute exposure covering the 1250-1600 A wavelengthrange (effective wavelength 1400 A), 730 star images can be detected,corresponding to a limiting ultraviolet magnitude of about m (1400) =10. Assuming nominal interstellar extinction values in this region nearthe galactic plane, this result corresponds to the detection of A0 Vstars to a distance of 300 pc and of B0 V stars to 1500 pc.Uncertainties in spectral classification and interstellar extinction forindividual objects are probably more significant than calibration ormeasurement errors. Most of the objects detected are identified withstars in the Smithsonian Astrophysical Observatory Star Catalog (1966),or the Catalog of Stellar Identifications (1979) or both, but 87 objectsremain unidentified (or are identified with late-type stars).
| Interstellar reddening and distance of Nova Cygni 1978
Observations of Nova Cygni 1978 at 7699 A (a potassium line) are used toestimate the nova distance. The distance seems to be 3.3 plus or minus0.6 kpc with a corresponding absolute visual magnitude at maximum lightof approximately -7.5. The nova is classified as a fast galactic nova onthe basis of its absolute magnitude at maximum light and the rate ofdecline towards minimum light. The color excess deduced from theobservations is reported, application of the distance-reddening law tothe nova is explained, and a composite light curve is presented.
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