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Submit a new article| Ca II H and K filter photometry on the UVBY system. I - The standard system A fifth filter (fwhm = 90 A) centered on Ca II H and K has beendeveloped for use with the standard uvby system. The filter, called Ca,is designed primarily for applications to metal-poor dwarfs and redgiants, regions where the uvby metallicity index, m(l), loses somesensitivity. An index, hk, is defined by replacing v in m(l) by Ca. Theeffects of interstellar extinction on the index are modeled anddemonstrated to be modest and relatively insensitive to spectral type.Observations of V, (b-y), and hk for 163 primary standards are detailedand transformed to the standard V and (b-y) system. A qualitativeanalysis using only the primary standards indicates that hk is moresensitive than m(l) over the regions of interest by about a factor of 3.
 
 
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| Constellation: | Caelum |  | Right ascension: | 04h23m21.83s |  | Declination: | -41°14'54.7" |  | Apparent magnitude: | 8.778 |  | Distance: | 374.532 parsecs |  | Proper motion RA: | 4.7 |  | Proper motion Dec: | 3 |  | B-T magnitude: | 10.857 |  | V-T magnitude: | 8.95 |  Catalogs and designations:
 
 
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