When you are outside doing astronomy, or any night-time activity that requires you to see as well as possible, any white light is a detriment. Every time you use white light, your eyes react. The pupils contract, making their aperture smaller, and a smaller aperture always means less light-gathering, whether we are talking about your eyes or your optical equipment.
A red flashlight allows you to see your star charts, find an eyepiece in your accessory case, or pick your way over telescope cables and other obstacles without affecting your night vision. The better your night vision, the more you can see in the eyepiece.
The Celestron Night Vision Flashlight uses two LED’s to provide variable red illumination. Use the thumb wheel to adjust the light as you need it. The square shape of the flashlight keeps it from rolling off of your observing table to the ground. A lanyard is attached so you can wear it around your neck. The Night Vision Flashlight is powered by a 9V battery (included).