• When you first get your night vision unit, get familiar with the focus adjustment of the front objective lens and the eyepiece ocular(s). On new units they may be stiff, but they will loosen with use.
• On most units the lens cap has a tiny hole drilled into it that will permit a minuscule amount of light to enter, permitting you to test it under daytime conditions. Remember though, never remove the lens cap and operate the unit during the daytime.
• Focusing a night vision unit is a two-stage operation. First, aim at an object and focus the front objective lens as best you can. Now focus the eyepiece ocular(s). This second stage is important as it sets up the unit to permit your eye to focus on the internal light amplification tube.

Always remember to guide new users through this two-stage focus process. First time night vision users often forget to make the critical eyepiece ocular adjustments.