Was your night photometric?
These pages contain the nightly observer reports from CTIO. Every telescope reports the sky conditions over the four quarters during the night. The sky is reported on a scale from 0 (clear) to 8 (totally overcast). The information from all the telescopes is then averaged by TelOps, and a final sky report is given. For instance, a report of 0-0-0-0 means the whole night was photometric. A report of 8-5-5-0 means that the first quarter of the night was totally cloudy, the next two quarters were partly cloudy, and the final quarter appeared to be clear. Seasoned photometrists would tell you that if a good part of the night was cloudy, the whole night probably should be considered suspect.