Permanent Cement Pier
The following is a description of how I built my cement pier
After too many nights of spending 1 - 2 hours setting up my LX90 for astrophotography using the drift alignment method, only to have the clouds appear as I was about to take my first shot, I decided that enough was enough. Time to build a pier. I decided on a cement pier, mainly due to the reduced cost factor but also because it would provide a rock solid mount for my astro-imaging pursuits.
To start with, I had to find a suitable location in my back yard that had a good all round view and a bit of space around it for a table and possible future small observatory. My better half and I agreed on a small patch where I could build my "falice" as she has come to call it.
I started by deciding on an exact location and marking it out with a stake in the ground. I needed a location where I could view a distant object for the purpose of training my LX90 drives. From this location I have a line of sight to some power poles about 1 km away which should do the job.
I marked out a square 1M x 1M around the stake and stared to dig. Notice the lovely soft topsoil. It was almost enjoyable until.............
...............i hit clay! It was going to be a long day indeed. Notice the spud bar at the top of the photo. I would use it to break up the clay and stones and then dig out the rubble. Luckily there was a cool Southerly breeze blowing. I ended up digging to a depth of 600mm.
Once the digging was done, it was time to prepare the hole for the cement pouring and provide some formwork for the pier itsself. In order to ensure a solid structure, I prepared some 10mm rebar in a simple double cross design with 4 vertical pieces sunk about 20cm into the ground and tied together at the top (see pic below). I bought a length of 300mm diameter Formatube and built a simple support frame to hold it in place.
At this stage I used a spirit level to roughly level the Formatube to ensure that it was sitting vertically. Even though I removed the Formatube during the pouring of the base, I wanted to have a rough idea of how it would sit.
After an enjoyable couple of hours of mixing 1 part cement, 2 parts sand & 3 parts blue metal, I finally filled the base. After letting it dry for 3 hours until it was reasonably firm but still wet enough to bond with the concrete in the pier, I put the Formatube back in place and made sure it was sitting absolutely vertically. I then spent another enjoyable hour of mixing more concrete and poured the pier.
Now for the tricky part. Sinking the aluminium base plate into the pier. I needed to ensure that it was oriented to true North (about 12 degrees East of Magnetic North in my location of Sydney, Australia). As the rebar played havoc with my compass at the pier, I aligned a stake in the ground about 10 metres away (true South) and used it as a compass point to align the plate.
After 3 days to allow the concrete plenty of time to set, I removed the formatube from the pier and assembled the mounting plates.
I levelled the plates by adjusting the 5/8" bolts that secure the base plate to the pier.
My "slaves" hard at work!!
This photo shows the construction of the pine log retaining wall around the pier. The plan is to have a raised, paved platform.
The finished product with Meade LX200 polar mounted.
I have since changes my imaging setup from a wedge mounted LX200 to a GEM (Losmandy Titan) mounted Takahashi FSQ106. Luckily, Losmandy sells an adapter which exactly matches the Meade mounting holes so there was no modification needed to my pier.
Materials (excluding aluminium plates)
Mounting Plate Design