Landolt Standard PG1323 on the 1.3m Telescope

We have spotted a peculiarity in observing the Landolt standard PG1323. It appears as though the light of a bright star (most likely Spica) outside the field of view is not properly baffled, causing the raised level of the background, as shown here:

In principle, this should not affect the count rate in the standard stars themselves, but, we do not recommend using this particular standard for your observations.