[looking up (Steve)]

Hello to all.
Just purchased a nice Sirius observatory and will need to install my heavy
Steel Pier. So given alot of you guys have done this before I thought I would ask the question. What would you think the depths and width of the hole as it would be supporting the big arse Pier, Meade 14inch SCT LX 200 and super wedge.
I would like to get away with the hole minimum size possible. I will attach some pics of the steel pier. Also could someone tell me what is the top section suppose to do of the pier the round bit with the bolts coming through.
Sorry this is very new to me this whole construction thing.
Look forward to your comments
Kind regards Steve