Explain the movements of 61 Cygni.
Edit: since I know you have never heard about 61 Cygni anyway, let me help you. 61 Cygni is a double star that is near enough to Earth for us to notice its movements compared to the more distant stars.
This awesome gif (posted on Wikipedia) shows steps of 1 year intervals, where you can see that 61 Cygni is moving against the "background" of other stars.
https://upload.wikimedia.org/wikipedia/commons/4/48/61_Cygni_Proper_Motion.gifOf course, it's entirely possible that these two stars are indeed just attached to the dome, and that something else explains this peculiar movement. Feel free to explain this to us if that's the case. :)
according to that gif, that tiny movement took 5 years, (2012-2017)...