Not sure who owns/live in the building, but here the moc:
Entrance suppose to be the 1x1 title.
Not accurate to an original Observatory since they open sideway, you can flip the sphere to reveal the scope and turn the head with the gear arm.
The scope need to be pulled out to extend.
I will admit it doesn’t look like a architecture at first glance and look like a deformed Darlek, but I hope you understand what it’s suppose to represent.