  Binary neutron star mergers are important to understand stellar evolution,
the chemical enrichment of the universe via the r-process, the physics of short
gamma-ray bursts, gravitational waves and pulsars. The rates at which these
coalescences happen is uncertain, but it can be constrained in different ways.
One of those is to search for the optical transients produced at the moment of
the merging, called a kilonova, in ongoing SN searches. However, until now,
only theoretical models for kilonovae light curve were available to estimate
their rates. The recent kilonova discovery AT~2017gfo/DLT17ck gives us the
opportunity to constrain the rate of kilonovae using the light curve of a real
event. We constrain the rate of binary neutron star mergers using the DLT40
Supernova search, and the native AT~2017gfo/DLT17ck light curve obtained with
the same telescope and software system. Excluding AT~2017gfo/DLT17ck due to
visibility issues, which was only discovered thanks to the aLIGO/aVirgo
trigger, no other similar transients detected during 13 months of daily cadence
observations of $\sim$ 2200 nearby ($<$40 Mpc) galaxies. We find that the rate
of BNS mergers is lower than 0.47 - 0.55 kilonovae per 100 years per $10^{10}$
$L_{B_{\odot}}$ (depending on the adopted extinction distribution). In volume,
this translates to $<0.99\times
10^{-4}\,_{-0.15}^{+0.19},\rm{Mpc^{-3}}\,\rm{yr^{-1}}$(SNe Ia-like extinction
distribution), consistent with previous BNS coalescence rates. Based on our
rate limit, and the sensitivity of aLIGO/aVirgo during O2, it is very unlikely
that kilonova events are lurking in old pointed galaxy SN search datasets.
