Which was about as big a telescope as could be fit in a C-141. Being the C-141 prototype, there were enough idiosyncracies in its configuration to make it not worthwhile to convert to the stretched C-141B configuration. It was one of just a handful of surviving C-141A's to not be converted back in the late 1970's early 1980's.
Sadly, that aircraft sits out in the weather at Moffett Field, CA. Most of the C-141's have been chopped up...I wonder if there are any more A models left?