For your set of 8x42 monocular, the exit pupil is five.twenty five. Try to find an exit pupil of five or higher if you need to use them in low light. The writer analyzed the thermal monoculars though hunting, viewing wildlife, and dealing on his ranch. Andrew McKean The Optics https://andynvxxw.ezblogz.com/59496437/5-easy-facts-about-thermal-monocular-described