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A cloud monitor instrument, sensing 8-14 microm infrared radiation, has been installed near McMurdo, Antarctica, in order to provide supporting cloud cover information for a high-resolution sky-viewing Fabry-Perot spectrometer experiment. Validation of the cloud monitor observations was performed by a 1 year long comparison with the available 6 h visual cloud observations, expressed in octas (obscured eighths of the sky). The agreement between visual observations and those of the cloud monitor is good--the variation being slightly over one step, or octa--except at the clear sky extreme, which the subjective visual observations tend to overestimate during dark and moonless conditions. Both visual observations and the cloud monitor measurements show an austral winter-summer difference with the winter being clearer.

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