If you are using a tripod mount a simple slab would be fine.
If you plan to do a pier fixed to the slab then a 1 metre deep x 1m cube and slab on top separated from the rest of the floor would be the go. Reinforce it with steel.
My observatory is built that way and the pier is rock solid.
You don't do one big floor slab as walking, vibrations etc can transmit to the scope.
Several piers into the ground conneted to one top slab as you mentioned sounds like it would work as well. But its mass you want so a M3 of steel reo in concrete and a pier bolted to that would be pretty hard to beat.
I have pavers for floor around my pier slabs so vibrations do not transmit to the pier concrete block ( a gap where they meet the pier).
Greg.
Quote:
Originally Posted by CDKPhil
I have Just found out that I will not be getting my tripod for the MX until March (if I am lucky ). The mount arrives on Monday, so I will have nothing to put it on. I do not want to wait till March to try out the MX so I thought I would put a pier in.
I have read in other threads that people use a solid block of cement about 1m3 for the base.
I was wondering instead of digging one big hole and filling it with cement and steel, I could use a post hole digger and put five columns into the ground?
One in each corner and one in the middle and a slab across the top, to join them together.
The dimensions of the columns would be 300mm dia by 1300mm deep and the slab would be 1000mm x 1000mm x 200mm. All re-enforced with steel.
I am not an engineer so I am asking would this be better than one big hole?
I did some quick calculations and the surface area in contact with the ground would be slightly more with the columns and it would use less cement than a hole that is 1m3.
All advice is much appreciated.
By the way I have a tractor to drill the holes 
Cheers
Phil |