With the roof works alsmost complete, the project now shifts to the interior and fit-out. First comes the mounting of the wall ring and dome structure, establishing the precise geometry for smooth rotation.

On the rooftop, I will lay a safe, weather-resistant walkway with integrated path lighting so night operations remain secure. The dome’s rotation drive will be installed and aligned, followed by comprehensive waterproofing to seal every penetration and transition. Inside, the build-up begins: insulation layers and a stable floor structure, then the wall insulation and sub-frame, ready to carry the interior cladding. The shutter drive will be mounted and tested for reliable opening and closing under wind load. After that, the parquet flooring goes in, and the insulated wall will be neatly clad for a clean, low-reflection finish. Finally, all electrical connections will be completed—power distribution, control wiring, and lighting—so the observatory operates safely, quietly, and ready for future automation. But lets start with the dome erection:

The Pulsar Dome

The observatory dome itself is a PULSAR 2.7 m Full-Height Dome Unit made from glass-fiber reinforced plastic (GFK) in eight bolt-together sections: four wall quarter-shells and four dome segments. The components are screwed together on site, forming a remarkably lightweight and easy to handle construction unit. My thanks to my friend Erwin Pilch for carrying the parts up together with me and helping with the assembly. Before he also prepared the structural calculations – resulting in just 135 kg of load to prevent a „flying observatory“ … The floor construction itself is about 190 kg, so the Dome should easily withstand the winds of change 🙂

Weather Sealing, Sealing, Sealing, …

One thing that seems underdone on the PULSAR domes is the weather sealing: the kit’s simple drip-edge profile is quickly overwhelmed by wind-driven rain, so water can enter at the dome–wall joint. I solved this by adding an external plastic sealing band around the seam and sealing it with silicone. Inside, I kept the original drip edge and added a continuous brush seal to block wind and insects. Since then, the joint has been reliably tight—even in gusty, rainy conditions.

Sealing the dome and wall segments with silicone added up to nearly 50 meters of joints—enough to make it a project in its own right. The payoff is a clean, continuous weather barrier that has stayed dry in wind-driven rain (… so far!).

Warm Feet Under a Cold Sky: Building the Floor

Inside the dome, the floor build-up starts with two layers of 20 mm of EPS insulation to reduce cold bridging and keep the floor „warm“. On top sits a grid of timber carriers that spreads loads and provides a solid, level base. Over the carriers I will install an 18 mm laminated wood decking and above it a continuous vapor barrier. The finish layer is a parquet floor—reused leftovers from our house build 11 years ago …
Around the pier, all layers stop short to maintain the vibration isolation.

I added a flexible rubber membrane to seal the gap around the pier at the connection to the foundation opening. It is bonded to the floor sheathing and it stays vibration-neutral while keeping insects and dust out.

The Walls

After a first attempt with 6.5 mm gypsum board over EPS—where the very first sheet cracked on the circular wall—I switched to a lighter, more flexible build-up: 50 mm rock wool insulation, a continuous vapor barrier, and a 4 mm plywood skin as the base layer. This stack follows the curve without stress, improves thermal and acoustic performance, and keeps moisture in check thanks to the vapor barrier. A white final finish will be added on top as the visible surface (still to be decided). The result is a warm, quiet, and robust wall that remains lightweight and service-friendly.

Power Supply and Distribution

The observatory’s power enters at a small central wall-mounted distribution box, which collects and fans out the circuits for the dome systems and all equipment. An emergency shut-off switch sits upstream of the consumers and cuts power to the entire setup with a single press—useful for storms, maintenance, or any irregular behavior.

Loads are connected via protected power strips , they provide a tidy, switchable outlet bank with integrated surge protection, so power supplies and chargers can be grouped and isolated quickly.

Selected devices sit on Wi-Fi smart plugs. This lets me power-cycle the moisture control (trying to hold the relative humidity below 75%), the lighting of the walkway to the observatory or schedule start-up sequences when needed—without climbing onto the roof at odd hours.

Put on the red lights …

Observatory lighting has to do two things at once: keep me safe at work and keep my eyes dark-adapted. Red light in the deep-red range preserves night vision far better than white; the key is to keep it dim, indirect, and glare-free.

My first tests with standard 60-LED/m strips were underwhelming: the light was spotty, with visible “dots” and uneven illumination. I’m switching to high-density COB (chip-on-board) LED strips that produce a continuous light line, are fully dimmable, and can provide both warm-white and red light. Mounted in aluminum channels and run on a separate, dimmable circuit, they deliver exactly the gentle, uniform glow I need for safe footing without interrupting dark adaptation.