A few weeks ago I was thinking of doing this very thing with a walnut tree I cut down in my observing area. Left the stump standing about 4 ft. tall until one day I just got sick of looking at it and finished it off with the chain saw.
Why not give it a try, Scott? It might work fine; for awhile anyway. You ought to be able to get a few years out of it at least.
Heck, an overturned 50 gallon drum to put your charts on, a couple of old school buses arranged as shields from the neighbor's lights and you'd have yourself a regular redneck observatory. Maybe put a real big tractor tire around the stump and you'd have a place to sit no matter where the scope was pointed.

We could start a redneck forum and try to outdo each other; but you'd have a big headstart.
Just kidding. I really do think it's worth a try.
Bob