Picture of the interior of UT4 acquired on 2017-08-15, when the dome was closed, the telescope parked, and all four lasers from the 4LGSF propagated. LGS1 and LGS4 are visible in the picture; their beam hits the cylindrical structure of an air-conditioning duct on the dome roof. The overall glow in the picture is evidence of the high amount of scattering of laser photons by the dome surface. All upper and lower lights in the dome were switched off during the test.