Hi Joe, There's nothing theoretically wrong with the idea, but in my day job I'm an engineer. It's in my DNA to pick at stuff until it either dies from the attention or stands up to the abuse. Everything you say is correct, but at the end of it all you have to have a telescope with enough resolution to pull a planet together (and you have to solve some giant stability problems). Otherwise it's just a diffused bit of light that may not even stand out from the background. That amount of resolution requires a huge objective--longer exposures don't make up for it. Someone who knows their Rayleigh would have to tell you just how big. Now that I've said all this, we'll find out that the Russians launched such a system for $273.