Skip, from what I hear and read, it seems that observatories on top of peoples homes in Florida are becoming the next big thing. I am not sure what the resale value of a house with one of those things would be, but they said it takes a lot of work to make the observatory absolutely stable. That is, a lot of extra framing, labor and materials.
I would never build one, but the idea did interest me. My house is located on top of a hill, and in the winter with the leaves off the trees, and its a clear day, I can see the snow capped mountains of what is known as the Rumford Highlands, which is about 100 plus miles away. I guess I got the place to build one should ever I choose too!
I have no intention of traveling from birth to the grave in a manicured and well preserved body; but rather I will skid in sideways, totally beat up, completely worn out, utterly exhausted and jump off my tractor and loudly yell, "Wow, this is what it took to feed a nation!"