European plans to build a massive optical telescope with a 100m mirror have been scaled back in favour of a 'scope with a mere 42m main reflector after the projected construction costs for the original dish reached €1.5bn.
However, the planned telescope is still bigger than the one planned by the US (30m), something scientists at the European Southern Observatory (ESO) admit has been a motivating factor.
More: http://www.theregister.co.uk/2006/08/07/shrink_giant_scope/