Complex sentence: ESO is also building a very large telescope E-ELT, and is doing so in Chile, if both next-generation telescopes were in the same hemisphere, there would be many astronomical objects that neither could observe.
Split into simpler sentences: ESO is also building a very large telescope E-ELT, and is doing so in Chile. If both next-generation telescopes were in the same hemisphere, there would be many astronomical objects that neither could observe.