What is the purpose of the M51 Instrument Light for the aiming circle?

The purpose of the M51 Instrument Light for the aiming circle is to illuminate the aiming circle in low light conditions. This feature is crucial for operators who need to perform accurate measurements and adjustments during nighttime operations or in environments with poor visibility. The illumination allows users to read the instruments clearly, ensuring precision in aiming and that all necessary readings can be taken accurately without straining or guessing. This enhances effectiveness in gunnery operations where visibility is critical for maintaining proper focus and accuracy.