Proba-3's first artificial solar eclipse
esa.int
esa.int
I wouldn't even know where to begin to tackle a problem like that.
The Amalgam in that story have fantastically better technology than we do, but this is certainly at the edge of what's practical for them. It's a fun idea though, I wonder how close we could get with our technology.
https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Ant...
Edit: and the already-flown Pathfinder : https://en.wikipedia.org/wiki/LISA_Pathfinder
2. They don't need to be. Most telescopes aren't trying to image the corona of the sun or another star.
3. Space-based telescopes are really expensive and have significant limitations on size, shape, mass, etc.