Two changes can imitate one cause
Covering a sensor blocks some of its view of the cold sky and can alter airflow. If the uncovered sensor is also the one receiving moonlight, a lower reading cannot isolate a cooling action of the light. The shelter and illumination changed together.
Build a paired comparison
Use matched sensors, the same mounting material and the same sky view. Change only a small, documented optical path where practical. Swap sensor positions and log wind, clouds and temperature over time. Test the shielding arrangement when moonlight is absent as well.
Interpret the energy balance
Surface temperature responds to absorbed radiation, emitted thermal radiation, convection and conduction. Incoming moonlight adds a small radiant input; open-sky thermal emission can remove energy at the same time. A temperature reading alone does not identify which term changed.