Flat earthers would say that it is a hologram or projected image of ISS made by NASA
How much shitty garbage nonsense they can give you instead of a simple and straightforward explanation.
When I observe the Universe through my telescope I feel that amazing feeling of exploring distant worlds. It's mind blowing that the light coming through your eyepiece was emitted thousands of years ago. The star is even not there anymore. And what about galaxies? It's even more amazing.
You are so closed minded. You will sit here on earth, look up in the sky and think about firmament and light glued to it. You cannot even explain events like Venus transition over the Sun surface, Eclipses (no matter Solar, Lunar or even eclipses of Jupiter moons), nothing. So pathetic. I pity you.
Another eye-opening experience (If you will pardon the pun ! LOL) is a visit to a local astronomical observatory.
Especially one on a low-light-pollution area such as Mc Donald Observatory in Texas.
Flat Earthers could learn a lot, especially on a night Star Party, but they probably are not interested.
Too far from their windows.
Also they would probably say all those stars , planets, nebulae, etc. are just a hologram projected on the dome by NASA.
At Mc Donald, they had some telescopes aimed at Saturn, a Nebula and some other objects.
Flat Earthers would probably say those telescopes just had pictures on them, painted by NASA.