Step by step

Step 1

Once you’ve chosen your observatory’s location, the next step is to calculate the internal size of the building. We verified our calculations by making a framework of canes and ensured that no part of the telescope moved outside the framework (except at the top).

Step 2

We engaged a local builder to do the groundwork and install the footings for the posts that support the main structure, as well as the concrete block pads on which our tripod would stand, and the stem walls of two courses of engineering bricks that support the floor.

Step 3

We damp-proofed the concrete pads and covered the ground with weed-block fabric on which we laid polystyrene insulation board. The floor is 18mm OSB3 board, supported on 95mm x 45mm timber joists, resting on damp-proof membrane on the stem walls.

Step 4

The inside walls are 11mm OSB3 board, which we fixed to the corner posts with wooden blocks and reinforced in the middle with vertical battens. Angle brackets are useful for securing the battens to the floor. (The batten at the top of the wall is temporary).

Step 5

Insulation will help control condensation inside the observatory. The walls have a layer of 25mm polystyrene insulation board, which is held in place by friction, then there’s an air-space between this and a sheet of vapour barrier that we stapled to the posts.

Step 6

The outer layer of the wall is pressure-treated shiplap cladding, secured over the vapour barrier layer. Any cut ends of timber will no longer be water resistant, so use a wood treatment on them in accordance with the manufacturer’s instructions.