Why use a red light for astronomy?

Human vision is produced with the help of Cones and Rods inside our eyes, cones for daylight and white light, while rods are used for low light and our night vision.

To preserve our night vision a red light is essential for your telescope accessory kit, the red light wavelength is hard for rods to absorb, and at this wavelength the cones will not be functioning which leaves the rods to work as normal and our eyes to stay dilated.

Within the rods and cones are photoreceptor proteins which differ in their sensitivity to different light colour and wavelengths, it takes time for these proteins to activate and absorb light in dark environments.

We want our eyes fully dilated and our pupils to allow as much light in as possible when stargazing, which takes approximately 20 to 30 minutes in darkness. At this point our eyes are at their optimum for night vision.