Hi narayan
good to see you are planning a pier .I have a eq6 mounted on top of my pier with a 8"scope guide scope & extras.not sure what soil you have but it does make a difference were iam the soil has been backfilled and is reactive clay which expands &contracts depending on the weather dry or wet.what i did was dig a hole 700 wide by 800 deep and lined the sides with coolite foam before i poured the concrete which took 10 bags to fill using quick set concrete,you have got to be fast as this stuff goes of .quick ,if you are going to put a housing around it later add some height to allow for the floor.my pier is dyno bolted in to the concrete using 8"dyno bolts and is rock solid
Hope this helps Cheers alan