but Allan's point is that the earth bound scopes cannot give high resolution (AO) imaging and reasonable field of view at the same time - and they certainly cannot do so in the visible/UV. Hubble can do it, simply because there is no atmosphere - even though the sensors are now quite ancient. It still does some things better than anything else (eg the deep fields and lensing studies) and it is quite startling to compare the best that ground based scopes can do with the equivalent from Hubble. For example, conventional ground based scopes show the large gravitational arc in Abell 2667 as a moderately resolved curved object. Hubble showed enough fine detail (0.05arcsec scale and mag28) that a moderately well resolved image of the source galaxy could be reconstructed - amazing.
http://arxiv.org/pdf/1410.6594v1.pdf
It will be great if it can remain productive just a bit longer.