Actually - a telescope of this size “looks out” to a distance of about 3 light years. So, with this thing coming straight at us at the speed of light it will impact earth in 2012. Perhaps the Aztec WERE onto something.
...Okay - just kidding. Obviously a telescope can only observe light that is impacting its lens. (Heck - this was probably a radiotelescope anyway!) Which would work the same way.
The one I get concerned about is the satellite we have parked between us and the sun (SOHO I think it is called?)that monitors sun flares, etc. Can see the “kill shot” coming and gives us 18 minutes (or whatever) of warning.
I hope I'm within arm's reach of my wife when it happens.
Cheers!