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CFH12K Filter Calibration Coefficients from Elixir The CFH12K photometric calibration coefficients are given below, assuming the Elixir normalization is used. Note that, for a mosaic camera, there is a ambiguity of how the different chips in a flat-field images are to be normalized. For Elixir, normalize a specific chip (04 in the case of CFH12K) to have a median value of 1.0. We force all chips to have the same number of input photons (by stacking the same numbers of input images) and normalize the other chips to match the normalization of the reference chip. The result is equivalent to treating the mosaic as a single, large collection of pixels. filter CΛ KΛ XΛ color B 26.017 -0.15 0.016 B-V V 26.220 -0.12 0.008 B-V R 26.190 -0.09 0.028 V-R I 26.185 -0.04 0.107 R-I Z 25.830 -0.03 - - Given m DN per second through the given filter, in an image taken at airmass z, for a star of the given color (in the target magnitude system), the magnitude M of a star in the Landolt (Johnson / Kron-Cousins) system is given by: M = m + CΛ + KΛ(z - 1) + XΛcolor It is also possible to define alternate color terms from those given above. Below we list all possible color terms for the four Johnson-Kron-Cousins bands BVRI and their CFH12K parameters. Since the colors of stars are highly correlated, these have been determined by fitting a line to the colors terms of the Landolt reference stars and adjusting the above parameters based on this fit. This adjustment does not strongly affect the zero point (CΛ) because stars of color 0.0 in one filter are nominally assigned to color 0.0 in all other filters. There is an obvious shift in the color slope (XΛcolor) resulting from the different typical ranges for different colors. filter CΛ KΛ XΛ color B 26.017 -0.15 0.010 B-R B 26.017 -0.15 0.008 B-I V 26.220 -0.12 0.014 V-R V 26.220 -0.12 0.007 V-I R 26.189 -0.09 0.031 R-I R 26.190 -0.09 0.010 B-R I 26.187 -0.04 0.050 V-I I 26.187 -0.04 0.026 B-I