  To assess the potential of a small telescopes for a high temporal resolution
astrophysics, we observed the field of FRB~121102 repeating source of fast
radio bursts on a 50-cm D50 telescope of Ond\v{r}ejov observatory, equipped
with a fast frame rate EMCCD detector. In a three nights of observations we did
not detect any optical flares from the source, which allows us to place an
upper limit of 10 mJy for a brightness of possible fast optical events on a
time scale of 10 ms. We also characterize the apparent brightness stability of
a field stars on the same time scale in order to investigate the potential of
such telescopes for detecting faint optical variability on a sub-second time
scales.
