The scales depicted here always bothered me. There is a curve to the sphere at the Jenolan's location that you just wouldn't see on something this size (radius of 1 A.U.)
Well, maybe it was on a hill...lol
The effects were quite good, and the episode really was about Scotty, but my inner nerd can't help but pick it apart...The thinness of the outer shell meant the sphere had a structure more tenuous than a soap bubble, but without the inner air pressure to hold the shape (being mostly vacuum inside). Also, the inside of the entry port looked to be at ground level; I would expect every time it was opened a huge rush of atmosphere would escape. There didn't appear to be a force field. One would expect walls to extend in above the atmosphere.