Construction of the POD Platform

Expecting a larger OTA and mount than my current C11/G11, I needed more headroom in my POD. Since my POD was sitting on the ground the simplest solution was to put a platform underneath it. Making a sunken floor would put my computer and eyepiece at a more comfortable height and make it easier to duck under the counterweight shaft!

I started with construction of the inner octogon that would bear most of the weight of the walls. I chose 2"x8" lumber, a larger size such as 2"x12" would have given even more headroom but would limit my reach when pushing the dome off onto the PZT. I have been doing mostly CCD imaging and have been happy with my choice. However, ignoring the PZT or having a small step available, I think a 12" lift would be about right for comfortable viewing through a 14" SCT.

Above is a sketch I made in order to figure out the size of the octogon and platform dimensions. It turns out the sides of the octogon (x in the diagram) are related to the inscribed circle diameter by D = 2.414x. The inner diameter of the bottom lip for the POD is 80", the inside wall diameter is 84" and the outer wall diameter is 89". I chose to match the inside edge of the 2"x8" with the inside of the POD lip, that made the outside of the wall still easily cover the farther corners of the octogon as seen in the right hand image. The pier offset was set 5" to the south. This is a balance between the amount of unobstructed zenith view and keeping the large OTAs from bumping into the south wall. With a C11 on a G11 mount I previously was able to have a 14" offset. The platform center is 6" to the north of the dome center giving the PZT structure on the north side an extra foot of deck to stand on.

Installed the octogon into the crushed stone base and leveled it. Due to a sloped yard all the attached "joists" are 2"x6", except three on the right (south side) which are the same lumber as the octagon (2"x8"). The most of the joists were attached with temporary spacer blocks underneath to keep them level.

More sloped yard solved by digging a trench on the west side (nearest). The imprint from the XL5 POD sitting directly on the ground for a year is clearly seen in the grass!

Joists complete late in the day. I replaced the spacer blocks with 2"x4" feet staked into the ground and screwed into the joists.

The deck boards are three quarters done well after darknees, but the sky is clear, so the scope cover comes off the C11/G11 and the "computer" pod gets dragged over for a night of imaging. Complete observatory renovation is not an excuse to miss rare clear skies!

Early the next morning the deck is completed.

The bottom floor boards are laid down on the crushed stone, each wiggled into position. Many are recycled from the previous floor.

OSB (Oriented Strand Board) is iteratively cut to just fit around the pier and snug up against the sides. Deck screws fix the OSB to the bottom planks.

The second half is installed to complete the observatory floor.

Reassembling the POD around the telescope and screwing the PZT to the deck are cinch now. And I didn't miss an hour of dark sky time during the overhaul, gotta love that POD!