The problem of fitting the Hubble Telescope into your fantasy setting is one of storytelling. You simply don't refer to it as the Hubble Telescope. It’s a bizarre artifact. The fantasy world is already full of bizarre artifacts, so that’s fine. It’s not magical, yet constructed using techniques and materials unknown to any artificer or wizard. To anyone in the world, it’s just a giant tube with a curved mirror in it and some thin sapphire plates on the side. Does it say “NASA” in giant letters on its side? Yes, but no one in the game knows that. It’s just some indecipherable script that literally no one, regardless of level, can decipher because not only does NASA not exist as a word, the Latin alphabet doesn’t exist.
The real world and fantasy world interacting is a trope that has existed for centuries.
A friend of mine played a D&D game where the party got sent to real world Earth. None of their magic worked. After they killed the first cop that stopped them, the half-orc barbarian promptly accident shot himself and died while examining the dead cop’s gun.
My friend said the adventure was hilarious.