Night vision devices gather existing ambient light (starlight, moonlight or infra-red light) through the front lens. This light, which is made up of photons goes into a photocathode tube that changes the photons to electrons. The electrons are then amplified to a much greater number through an electrical and chemical process. The electrons are then hurled against a phosphorus screen that changes the amplified electrons back into visible light that you see through the eyepiece. The image will now be a clear green-hued amplified re-creation of the scene you were observing.

A regular scope has an objective lens and eyepiece adjustment. First, adjust the objective lens to perfect the image. Then adjust the eyepiece to your eyesight. In binoculars or goggles each eyepiece must be adjusted separately. To do this close your left eye and adjust the right eyepiece. Then open you left eye and adjust the left eyepiece to get a full contrast image. Some night vision goggles require objective focusing first, and then adjusting the eyepieces.

All Starlight scopes need some light to amplify. This means that if you were in complete darkness you could not see. Due to this we have a built in infra-red illuminator (IRI) on all of our scopes. Basically what an IRI does is throw out a beam of infra-red light that is near invisible to the naked eye but your NVD can see it. This allows you to use your scope even in total darkness. The IRI works like a flashlight and the distance you can see with it will be limited. This allows our IRI to extend out to 100 yards However, because of the power at a short distance the IRI may cover only 40—60% of the viewing area.

No, you cannot use your analog night vision during the day.

Yes, digital night vision can be used 24/7. 

The image is in black and white with adjustable brightness and contrast. 

No, there are no thermal imagers able to look through glass because glass does not let infrared radiation within 8-14 ɥm pass.

It is not recommended that the thermal imager with open lens cap is pointed at powerful sources of energy (unit emitting laser radiation or the Sun), because it may negatively impact the accuracy of the thermal imager. Do not use your thermal unit at temperatures exceeding +50 °С as high temperature may damage the unit.

Due to various thermal conductivity, objects (surrounding environment, background) under observation get warm faster at positive temperatures, which allows higher temperature contrast and, thus, quality of the image produced by a thermal imager, will be better. At low operating temperatures objects under observation (background) normally cool down to roughly equal temperatures, which leads to lower temperature contrast, and to image quality (precision) degradation.