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This is slightly off topic,,,please forgive. I had never heard we have poor red response (assume meant as when dark adapted) so I did some surfing. I came across an article that was very interesting. If this article is correct we're all running around with our red flashlights degrading our dark adaptation every time we turn one on. Read and see! No pun intended Also to see red it appears you need to look directly at what you looking at. The center of your retina is all red cones. Interesting read.

oops...forgot the link http://www.stlplaces.com/night_vision.html

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Well, I'm afraid that the article is a little inaccurate in a few areas (spelling among them). While *any* light used for chart illumination impacts night vision, *DIM* red light is still the best kind to help preserve dark adaptation. This has been fully demonstrated by a number of scientific studies (I can give a number of published references if need be). The light should be adjustable in brightness or be just barely bright enough that you see a sort of very vague reddish-brown color on a white piece of paper. If the paper looks a nice brilliant red, the light is *too* bright. Using a light much brighter than the point where you can just barely detect the reddish color on white paper can cause a signficant reduction in your dark adaptation. Even with such steps, after extended chart reading with a minimal red light, there can be a short "re-adaptation" period to get back your optimal level of night vision. Bright red lights are definitely a no-no (unless you are maybe using them for navigation as you walk around). Clear skies to you.

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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info

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