And construction and operating costs are not only astronomical, they are cosmological. And too far south, the summer skies are washed out by the midnight sun.

Incidentally, different hemispheres look at different SKIES at the SAME time. The ideal spot, weather and insolation-wise for a big new optical instrument is a high mountain on an oceanic island in the trade wind zone, a southern hemisphere analog to Hawaii. I don't think there is a viable candidate. Chile is about the best we can do.

BTW, you might want to review my previous post. I added some edits while you were typing.