  The NASA's Double-Asteroid Redirection Test (DART) was a unique planetary
defence and technology test mission, the first of its kind. The main spacecraft
of the DART mission impacted the target asteroid Dimorphos, a small moon
orbiting asteroid (65803) Didymos, on 2022 September 26. The impact brought up
a mass of ejecta which, together with the direct momentum transfer from the
collision, caused an orbital period change of 33 +/- 1 minutes, as measured by
ground-based observations. We report here the outcome of the optical monitoring
campaign of the Didymos system from the Danish 1.54 m telescope at La Silla
around the time of impact. The observations contributed to the determination of
the changes in the orbital parameters of the Didymos-Dimorphos system, as
reported by arXiv:2303.02077, but in this paper we focus on the ejecta produced
by the DART impact. We present photometric measurements from which we remove
the contribution from the Didymos-Dimorphos system using a H-G photometric
model. Using two photometric apertures we determine the fading rate of the
ejecta to be 0.115 +/- 0.003 mag/d (in a 2" aperture) and 0.086 +/- 0.003 mag/d
(5") over the first week post-impact. After about 8 days post-impact we note
the fading slows down to 0.057 +/- 0.003 mag/d (2" aperture) and 0.068 +/-
0.002 mag/d (5"). We include deep-stacked images of the system to illustrate
the ejecta evolution during the first 18 days, noting the emergence of dust
tails formed from ejecta pushed in the anti-solar direction, and measuring the
extent of the particles ejected sunward to be at least 4000 km.
