Speaking for myself, most of what I have written is based on my own dissection of bull's eyes from the abattoir in the village I grew up in when I was about 13. I was given a dissection tool kit which used to belong to my aunt when she was at uni.
With a battery, you could stimulate the exposed muscles to contract the iris and lens, providing the eyes weren't too old.
Book learning on the subject at secondary school/high school didn't occur for a couple of years after that iirc.
Well when you start looking at the Earth through those Bull's eyes, let me know. For now, keep looking through your own and try and understand them. Try and understand that they are not capable of telling your brain anything but are a looking glass for your brain to decipher what the hell is going on outside of the enclosed control room inside your skull by use of tehse windows to the world.
When you focus your eyes on a reference point, it's like trying to discard a wide angled telescopic view, because your brain is also aware (through those eyes) of light hitting all parts of that convex eye.
So when you focus on a reference point, you are trying to train your eye like a scope on a sniper rifle. The centre of your crosshair is your primary focus and you gain a sort of tunnel vision whilst concentrating on that.
Your naked eye is looking in ALL directions, even when you're focused on a reference point. It's taking in all light that reflects onto it from all directions.
The sky is lighter than the sea because you can look up with more angle than you can look down.
In the sky your eye takes in more light. Looking out to sea, your eye takes in much less because it's angle on the convext bottom of it hits the sea as you look out whilst your convex top takes in more light from a larger angle of sky.
The centre point of your eye marries them up and you see your horizon.
Anything moving towards that horizon will also transfer the same reflected light to your eye.
The bottom of your convex eye will take in less light as your eye skims the water and more light as the top skims the sky, so anything in that skyline will stand out to your eye as opposed to anything closer to the water. Hence, why the hull of a ship disappears before the mast.
You still have left and right angles that take in light which cancel out as equal light, meaning you don't see any noticeable change in side angles of light towards your eyes.
The whole reason as to why this happens should be clear to anyone in that at sea level, the air is denser on the horizontal than it is on the vertical angle, meaning it's harder for reflected light to reach your eye than it is for reflected light to hit it from a vertical position.
Stop messing about with Bull's eyes. In fact try not to stand around Bull's at all and you have a better than average chance of not reeking of the stuff they deposit out of their back end.
Posting up eye diagrams is similar to all the rest of the stuff you people do and pretend you're experts. Parrots and copy and paste specialists, as well as artists specialising in Bull excrement.
The only difference between you people and a parrot, is, a parrot can be entertaining when mimicking someone's voice or telephone, etc. You people simply mimick text and diagram's. It's not smart. It's not even remotely intelligent and it don't impresser me much.