Southern Standard Stars for the u'g'r'i'z' System:

CTIO u'g'r'i'z' Filters

Based upon the Custom Scientific transmission curves for the u'g'r'i'z' filter set, the CTIO quantum efficiency curves for the Tek2k detectors, and the aluminum reflectance tables of Bennet et al. (1963), we have made a preliminary estimate for the response curves of the CTIO-0.9m+Tek2k+u'g'r'i'z' filter system. These curves will be updated as better data on the CTIO u'g'r'i'z' filter transmissions and the Tek2k#3 quantum efficiency become available.

The following plots compare the response curves for the CTIO-0.9m+Tek2k+u'g'r'i'z' system with those from the USNO-1.0m+Tek1k+u'g'r'i'z' system which was used to define the Northern and Equatorial u'g'r'i'z' standards:

Note that the CTIO and USNO u'g'r'i'z' plots are very similar. This result is consistent with the small values we measure for the instrumental color term coefficients for our CTIO-0.9m data.

ASCII tables of for the CTIO-0.9m+Tek2k+u'g'r'i'z' responses can be found here:

Custom Scientific u'g'r'i'z' filter transmission curve data: Strictly speaking, these curves are for the University of Wyoming u'g'r'i'z' filter set. Unfortunately, accurate versions of the CTIO u'g'r'i'z' transmission curves are presently only available as hardcopy plots. The CTIO u'g'r'i'z' filters were also manufactured by Custom Scientific, and plots of the above transmission curve tables match well what is shown in the hardcopy plots of the CTIO transmission curves. CTIO plans to re-measure their u'g'r'i'z' curves in the near future; when the resulting data tables are made available, we will updated the contents of this webpage.
CTIO Tek2K#3 quantum efficiency data:
Aluminum reflectances from Bennet et al. 1963, Journal of the Optical Society of America, 53, 1083, as reproduced in Kneale 1994, "Functional Specification for the Gemini Coating Plants," SPE-TE-G0043:
Last updated: 19 September 2007
J. Allyn Smith (
Douglas Tucker (
Sahar Allam (

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