Which color of light source is recommended to preserve night vision when consulting charts or equipment settings?
Answer
Red light
To protect the hard-earned night vision once the eyes have adapted, all sources of bright light must be avoided, or filtered appropriately. If navigation or checking equipment settings is necessary, utilizing a dedicated red-light flashlight is the preferred method. The reason red light is recommended is that it affects the eye's dark adaptation process significantly less than white or blue light does. If only standard white light sources are available, they should be modified, perhaps by covering them with red cellophane or employing a built-in red filter feature often found in astronomy applications.
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