Is there a FE-explanation why the sun is partially obscured during sunrise/sunset?
This here assumes that the sun is a point-source of light.
https://wiki.tfes.org/The_Setting_of_the_Sun
Many different models have many different explanations. I'll give you a few.
1. The sun is not partially obscured during sunset. The video below proves it:
2. The sun is partially obscured during sunset which is proof that the earth is flat:
3. The sun is obscured because of the dome
4. The sun is obscured because of the refraction of light
These are just silly.
Video #1 lacks a solar filter, illustrates a solar glare shrinking as the intensity of the light decreases. In the video he claims you don't need proper equipment, he is simply wrong. See this video for proper treatment of filming the sun.
Video #2 coin illustration has 2 main problems: 1) the view of the desk is not parallel to the top of the desk, we can see that it is angle up slightly in relation to the top of the table. 2) the coin is contacting the surface of the desk, nobody I'm aware of has suggested the sun touches the surface of the earth at sunset, instead the claim is the sun is above the earth. Most FE claims I have seen say the sun is 3000 miles above the earth
Video #3 doesn't match any of the claimed FE models. This shows a light source outside a lens of some sort and way past the Tropic of Cancer or Tropic of Capricorn. Not even close to any models. For good reason, it significantly modifies the apparent location of the sun.
Video #4 if just incorrect understanding of optics. He starts out talking about how much water is in the air. Then shown water in a glass or pool and tries to draw us to think these are congruent. They are not. Water vapor in the air is in no way the same as a water in a glass or water droplets suspended in the air. He says "water causes refraction bending the image downward and magnifying it". This is just not the case. Just like the glasses on my face, the
shape of the object with different refractive index determines what happens. His example of a glass of water with a pencil would shrink the apparent size of the pencil if the surface of the glass were concave instead of convex. Further, there is no such thing as "downward" to light, this is utter nonsense. This video is so many layers of wrong. It's difficult to determine if the creator of the video is not very smart or knowingly dishonest. He actually used an example from a TV news crew showing the Chicago skyline
raising up due to a lens, then shoed a mocked up an experiment
lowering the sun. Clearly, the portion of the lens being used is important. Be consistent.
To be more scientific, let's take the Flat Earth idea and make some predictions for the sun's position using the popular Gleason map. Let's choose a viewer's location on the earth on the Tropic of Capricorn, on December 21. This location and date is very favorable to the Flat Earth idea. Now calculate the sun's predicted location when the sun is at it's farthest point from the viewer. It will be on the Tropic of Capricorn on the opposite side of the flat earth's plane. The Tropic of Capricorn has a radius from the north pole of 7567, diameter is 15134. The sun is 3000 miles up directly above the Tropic of Capricorn. This gives us a triangle where we know two sides and the angle between them is 90 degrees. Use your geometry or use an online triangle calculator to plug in 15135, 90 degrees, and 3000. Solve for the triangle. This gives us an angle of 12.212 degrees. Note: this is not at sunset, this is the most extreme distance in the middle of the night.
Now we have made the prediction we can test to see if it matches observations. I'll leave that as a future exercise.
Edit: After rereading and thinking about the math I was concerned the angle was too small so I verified the calculations and the angle was, indeed, too small. The original angle I quoted was 1.137 degrees, the correct angle is 11.212 rounded to the thousands place. I verified this on 3 online calculators listed below.
https://www.calculator.net/triangle-calculator.html?vc=&vx=3000&vy=&va=90&vz=15135&vb=&angleunits=d&x=44&y=13http://www.mathwarehouse.com/triangle-calculator/online.phphttps://keisan.casio.com/exec/system/1273849674