I finally found the time to build an observatory in my garden in 2015. As part of the observatory of course I needed a pier to mount scope on. The following details the piers construction.
Here is the shopping list:
(as of Summer 2015)
|Steel rods||1m x 3||£6|
|Steel rod||2m x 1||£2|
|Aluminium discs (from ebay)||20cm diameter, 1cm thick||£10 ea|
|Steel tube (from ebay)||1m x 16cm diameter||£65|
|Wooden Disc||2.5cm x 12cm diameter||–|
|Nuts and Bolts||M10 x 8||£10|
|Nuts and Bolts||M12 x 1||£2|
Although the above costs are approximate the total cost came in at around £135.
I started the observatory by roughly positioning the square hole for pier, this hole I lined on 4 sides with polystyrene (roof insulation I had lying about), to act as a vibration dampener. Various online articles suggested you needed 1m3 of concrete and an air gap. I took a gamble on this and it has appeared to pay off (when I’m imaging and moving around there is no noticeable wobble when guiding on PHD, yes I did stand in the observatory in my warm clothes jumping up and down!).
I then inserted 3 steel rods (100cm long) into the concrete (30cm deep) and one central steel rod (150cm long) and then slipped the steel tube over the top and levelled everything.
Here you can see down the tube and the 3 shorter rods and 1 long central rob.
Next I created a sacrificial template out of some scrap ply to hold 4 bolt holes. The bottom piece of ply would remain in the pier forever and be set in the concrete. The top piece of ply will be removed once the concrete is set. This top piece has a large hole in the centre to pour the concrete into the steel tube.
Once the floor was set I filled the steel tube with concrete, tampering as it filled up. When I reached the top I was careful to level off to the top of the steel pier tube. I left the top piece of ply in place to keep the bolts spaced correctly and keep any muck off the bolts.
I then painted the pier with some undercoat and removed the top bit of ply to expose the nice clean bolts.
I bought 2 identical aluminium discs. One to place on the top of the pier with 8 holes. The 4 holes nearer the centre of the disc are for the 4 pier bolts. The 4 outer holes are for the top aluminium disc bolts.
Final assembly is to place the top disc in place. I then used 4 bolts to make this adjustable, so its perfectly level. The top disc has a 12mm central hole for an M12 bolt (to bolt to the EQ6). I did have a piece of aluminium for the bolt, but in the end I did not have the tools to cut this for the base of the EQ6, so I used another piece of ply painted white. This seems to work fine and is solid (after all its bolted securely to the aluminium, which is doing the real work).
Finally you can see the final pier with a box for the electrics and USB ports. Seems to work well, so far…