In the past I have done a Sun observation experiment involving multiple people in different parts of the world observing sunspots at the exact same time trying to detect parallax. I found no parallax meaning that the Sun is far away and that the Earth s round, but some flat earthers said that the experiment was inconclusive due to low image quality or some nonsense like that. I also have a thread to plan a redo of that experiment involving more people, but very few people have the proper equipment. This is why I am proposing this next experiment.
This experiment is the same as the Sun observation one, except it's the Moon that we will be observing. The great part about this is that even on a round Earth the parallax should be great enough that it should be possible to calculate the distance to the Moon, assuming that the images have a high enough quality. If the Earth is round then we should see only this tiny amount of parallax and the exact amount of parallax should put the Moon at roughly 238,900 miles away. On a flat Earth we should expect the parallax to be so great that we won't see the same sides of the Moon and the phases should be different for everyone. If anyone disagrees with these predictions then you can present your own. That includes you flat earthers.
What I need is anyone with the equipment to photograph the Moon. Even a camera with a god zoom on it would work. Ideally I would like the image to be as zoomed in as possible while still showing the whole Moon, but if you can't zoom in that far you can still participate. I would like as many flat earthers to participate as possible. I won't plan the exact date until I have a good few volunteers so we can work out time zone and weather related stuff so I can get as many of the volunteers as possible to be able to participate. If you do volunteer then note that it's not a commitment, it's just letting me know that you are willing and capable of participating.