Hey PFers. I'm just wondering what your thoughts on a High Altitude Telescope are. What I mean is pretty much a telescope on a platform suspended in air on balloons at 40,000+ feet. The whole thing would be solar powered, with a couple of engines capable of station keeping, with the appropriate support hardware for data transfer, communications, ballast, etc. My thinking was that something like this would be several orders of magnitude cheaper than space telescopes such as the HST, and much much easier to service, upgrade, etc, while having nearly the same capabilities. At 40k-50k feet your above about 90% of the atmosphere, greatly reducing it's effects. So, is my thinking somewhat correct? What are some obvious downsides? Obviously keeping a telescope stationary and on target while on a platform in the air would require a little more work than my own mount and tripod I use with my personal scope, but it doesn't seem unachievable given that we have giant multi-meter telescopes with movable mirrors and such currently.