A faint image may build up toward visibility for as long as six seconds if you can keep it at the same spot on your retina for that long. Doing so is quite contrary to instinct, because in bright light fixating on something tends to make it less visible with time. It also may help to explain why bodily comfort is so essential for seeing faint objects. Fatigue and muscle strain increase eye motion. Using high powers.
Conventional wisdom holds that low power works best for deep-sky viewing.
But as Clark proved after digging through laboratory vision studies, this assumption is usually false. High powers should do better on many faint deep-sky objects. The reason is subtle but key to understanding how low-light vision works, so we'll go into some detail. The essential point is that the eye, unlike a camera or other purely mechanical lens system, loses resolution in dim light. Studies show that the eye can resolve detail as fine as 1 arc minute in bright light but can't make out features smaller than about 20 or 30 minutes wide when the illumination is about as dim as the dark-sky background in a telescope.