  The first on-sky results obtained by CANARY, the Multi-Object Adaptive Optics
(MOAO) demonstrator, are analysed. The data were recorded at the William
Herschel Telescope, at the end of September 2010. We describe the command and
calibrations algorithms used during the run and present the observing
conditions. The processed data are MOAO-loop engaged or disengaged slope
buffers, comprising the synchronised measurements of the four Natural Guide
Stars (NGS) wavefront sensors running in parallel, and near Infra-Red (IR)
images. We describe the method we use to establish the error budget of CANARY.
We are able to evaluate the to- mographic and the open loop errors, having
median values around 216 nm and 110 nm respectively. In addition, we identify
an unexpected residual quasi-static field aberration term of mean value 110 nm.
We present the detailed error budget analysed for three sets of data for three
different asterisms. We compare the experimental budgets with the numerically
simulated ones and demonstrate a good agreement. We find also a good agreement
between the computed error budget from the slope buffers and the measured
Strehl ratio on the IR images, ranging between 10% and 20% at 1 530 nm. These
results make us confident in our ability to establish the error budget of
future MOAO instruments.
