I have three base rings for a technical innovations ProDome. The rings include a door and all are complete. They are in new condition. All you need for a Pro Dome is the dome and that will add a foot and since hese rings will raise the dome a little over three feet you will have about a five foot base; just put the dome on them. I will sell for $300 cash, or trade for $300 worth of astronomy or photographic stuff.
These rings cost about $3600 total several years ago. If you plan to build an observatory you should look into this.
I live in the East SF Bay Area.