From those observations, you can deduce how the solar system operates.
It's not even all that difficult.
If it was that easy, people would have understood the relationship between the Earth and sun hundreds of years ago. Oh wait, they did that didn't they. Never mind.
It's kinda interesting really.
Certainly we understood the motion of sun, stars, planets, etc
relative to Earth hundreds...possibly even a thousand or more years ago.
But it was only in the time of Galileo, in the 1600's (arguably) that we finally figured out that the sun was at the center and the Earth orbited around it. That's actually quite a tough thing to prove.
That's weird because if you believe FET, then conclusively proving that the sun ISN'T at the center of the solar system should be trivial...and you'd think that someone as undoubtedly smart as Galileo would have figured it out.
The thing that truly amazes me about Flat Earthers as a group is that they need such an insanely complicated system to explain simple stuff.
In RET, the motions of all of the stars, planets, sun and moons can all be explained from one tiny equation (F= m1 x m2 x G / (d x d)) - that one SIMPLE thing explains the shapes of these bodies, and almost all of their motions. It explains sunsets, eclipses, the phases and orientation of the moon, syzygy's, comets, asteroids, galaxies, black holes, the length of the day, the seasons, the "midnight sun" over the poles...SO much of what we see...all with just one incredibly simple equation. We don't require planet-wide conspiracies shared across hundreds of years and governments who hate each other.
RET is *SO* simple, so incredibly elegant. All of that complexity springing simply and (almost) flawlessly from a single equation.
(Almost - because it took Albert Einstein and general relativity to explain the precise details of the orbit of Mercury.)
In FET, all of those things move in bizarre ways for no good reason, the earth accelerates upwards with no observable power source, an extra object (the shadow object) has to be introduced to explain lunar eclipses - I still don't understand how they can claim moon phases. Even the tiny fraction of these things that are well explained require all manner of carefully tuned mechanisms.
Why do the FET planets move in EXACTLY the way they need to move in order to make it look precisely as though they, and the Earth, are traveling in simple ellipses around the Sun? In FET, their paths are (to say the least) bizarre - changing direction completely for no obvious reason - doing crazy complicated dances that just HAPPEN to operate exactly as if they were being pulled around (along with the Earth) by the sun's gravity. Yet the stars do no such thing...they obey even crazier rules (which don't actually work BTW) to make them swirl around in opposite directions in the Northern and Southern hemiplanes (without doing some kind of opposite-direction flow at the equator).
The weirdest part is that FET has the hardest time explaining the simplest phenomena - and the "laws of nature" that it requires seem to be carefully designed to make it look EXACTLY as if the world is round! The sheer unlikelyness of a Flat Earth having laws of physics that make it appear to be round to every single test you can apply to it...that's astonishingly unlikely.
The sheer implausibility of the towering pile of wobbly, unprovable, debunkable, self-contradictory assumptions that is the FET are it's ultimate disproof.