Of course, when galaxies and nebulae are important, you must have a dark site. If, like me, you already live far out in the boonies, your home environment might be perfect. Otherwise, if you can commute, buy some land in the middle of nowhere, where real estate is inexpensive. Solar panels and battery storage can preclude the need to spend a fortune erecting poles to connect to the grid. Don’t close until you’ve spent a night camping there. If one sky-direction must be blocked, sacrifice the north.
Next decision: type and size. I built a big roll-off roof observatory in the mid-’80s. No one helped me, and I made major mistakes. I put the roof on swiveling casters. Don’t do that. I had to jack it up and replace everything. I also thought the roof’s wheels would roll on the wooden wall tops. Wrong again. When parked, the heavily loaded casters created depressions and wouldn’t readily climb out of them. I jacked everything up again and topped the walls with thin steel plates. It was harder than it sounds.
I also learned that everything needs to be periodically greased. And that a reversible half-horsepower DC motor was best for moving the enormous weight. And to use chains, not cables. Also, the 12-by-20-foot (3.7 by 6 meters) building was excessive. Do yourself a favor and go smaller.
Then, last year, having moved to even darker skies and now significantly less poor, I gladly paid Explora-Dome to install an 8-foot (2.4 m) motorized dome on their square building. Everything all together — the dome, building, and labor — totaled under $10K. Another few thousand covered the masonry foundation and pier, and the end result was my big f/6 equatorial reflector in one observatory (the roll-off) and apochromatic refractor in the dome.
Shuttling back and forth from a dome to a roll-off provides a great A/B comparison. Yes, a dome looks cool. But a roll-off exposes the entire sky, letting occupants stargaze or use binoculars while waiting their turn at the scope. You can’t do that in a dome.
The bottom line is: Don’t ever abandon your observatory dream.
I’ve skipped the part about how snakes like to nest in them.