NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2022 Mar 14, 10:38 -0700
Howard G, you wrote:
"Actually the opposite is true. Cones are packed in the centre and are used for colour and resolution. Rods are in your peripherial and are sensitive to movement and low light. An old trick I learnt whilst trying to find low light stars at night is to Not Look Directly at it as you people are doing with Venus. It will disappear."
As Ed Popko has already mentioned, the phenomenon you're describing is called averted vision, and it's an important tool for spotting faint objects, whether stars (either by naked eye or through a telescope) or lights on vessels at great range, in darkness. Just to clarify, this does not apply to Venus in daylight, and in fact averted vision would work against you if you're looking for Venus in daylight. As I and others have mentioned, instead of averted vision, to see Venus in daylight naked eye, you need to look straight at it, which means you need some method for sighting along the exact azimuth and altitude. Once you get the image of Venus on the cone-packed fovea of your eye, you can see it easily, and it's shockingly obvious. But if you then lose it, it's equally amazing how hard it is to pick up again without going through the same azimuth and altitude alignment process that you used to find it in the first place. So why doesn't averted vision work on Venus? I don't know. It has to be some property of human vision in bright light, which apparently does not have a common name.
Frank Reed