  Ground-based photometry of bright stars is expected to be limited by
atmospheric scintillation, although in practice observations are often limited
by other sources of systematic noise. We analyse 122 nights of bright star
($G_{mag} < 11.5$) photometry using the 20-cm telescopes of the Next-Generation
Transit Survey (NGTS) at the Paranal Observatory in Chile. We compare the noise
properties to theoretical noise models and we demonstrate that NGTS photometry
of bright stars is indeed limited by atmospheric scintillation. We determine a
median scintillation coefficient at the Paranal Observatory of $C_Y = 1.54$,
which is in good agreement with previous results derived from turbulence
profiling measurements at the observatory. We find that separate NGTS
telescopes make consistent measurements of scintillation when simultaneously
monitoring the same field. Using contemporaneous meteorological data, we find
that higher wind speeds at the tropopause correlate with a decrease in
long-exposure ($t=10$ s) scintillation. Hence the winter months between June
and August provide the best conditions for high precision photometry of bright
stars at the Paranal Observatory. This work demonstrates that NGTS photometric
data, collected for searching for exoplanets, contains within it a record of
the scintillation conditions at Paranal.
