  The Cherenkov Telescope Array (CTA) is the next generation very high energy
gamma-ray observatory covering the 20 GeV - 300 TeV energy range with
unprecedented sensitivity, angular and energy resolution. With a site in each
hemisphere, CTA will provide full-sky coverage. Four Large Size Telescopes
(LSTs) in each site will be dedicated to the lowest energy range (20 GeV - 200
GeV). The first LST prototype has been installed at the CTA Northern site
(Canary Island of La Palma, Spain) in October 2018 and it had been since then
in commissioning phase. LST1 is located at about 100 m from MAGIC, a system of
two 17m-diameter Imaging Atmospheric Cherenkov Telescopes designed to perform
gamma-ray astronomy in the energy range from 50 GeV with standard trigger (30
GeV with SumTrigger) to 50 TeV and whose performance is very well established.
The co-location of LST1 and MAGIC offers the great opportunity of
cross-calibrating the two systems on an event-by-event basis. It will be indeed
possible to compare the parameters of the same extensive air shower
reconstructed by the two instruments. We investigated the performance that
could be reached with combined observations.
