It's linear, so if it is 25 times closer then the telescope can be 25 times smaller. At 4.37 light-years we'd need an 18 kilometer telescope to image at Jupiter

It's linear, so if it is 25 times closer then the telescope can be 25 times smaller. At 4.37 light-years we'd need an 18 kilometer telescope to image at Jupiter-sized planet at 100x100 pixel resolution. If you only wanted 10x10 resolution you could get by with a 1.8 kilometer telescope. Wikipedia has more: https://en.wikipedia.org/wiki/Angular_resolution https://en.wikipedia.org/wiki/Angular_resolution. The Rayleigh criterion is the equation to calculate this.