Permanent pier mount tip: you don't need to level a pier to get accurate polar alignment.
The reason I mention this is I've seen a number of leveling bolts /plates on various piers and have wondered why.
While it is true that while you will not get an adjustment in Altitude having a secondary effect of a change in Azimuth and vise versa) but a couple of iterations will easily fix that.
What you do get is three or four leveling bolts taking the entire weight of the mount/telescope/counterweights and acting like springs...not good if rigidity and a high natural frequency of vibration of the system is your goal.
Hope that helps if you are contemplating pier mounting a telescope
Peter, I do understand what you are saying, and although I to have this type of arrangement on my pier, due to the size and thickness of the plates, and the diameter of the anchoring bolts, I find there is really no vibration problems to worry about, it is rock solid, and carries all the weight easily.
Good point though, as i have to admit i spent a long time getting these plates level
Leon, for sure there often very good reasons why you need to go down that path.
When you run the math, the bending moment of a 1/2" bolt compared to a 6 to 10" pier is not insignificant, and the frequency of the system is set by it's weakest link (comparatively thin bolt), hence my tip
Here is my solution Peter. I leveled the pier once with the eight 12mm bolts at the bottom of the pier. The uncluttered top gives me maximum travel before an equatorial flip is required. The tapered gussets minimise any resonance or ringing. The mount copes quite well with 20Kg refractors even in strong winds. I doubt if it would with a large newtonian 10" maybe 12" no way. The belt drives are far better than the usual spur gears.
This is one of the few cases where near enough is good enough. The mount is fixed, so it's a once off adjustment, and a few more iterations don't matter. However, with a portable mount, it definitely saves time if the mount has a decent levelling system.
Geoff
Leon, for sure there often very good reasons why you need to go down that path.
When you run the math, the bending moment of a 1/2" bolt compared to a 6 to 10" pier is not insignificant, and the frequency of the system is set by it's weakest link (comparatively thin bolt), hence my tip
Peter makes a valid point of course. But to understand all the effects introduced by suspending the pier on levelling bolts, you've also got to consider (among many other things) the distance between the pad and the pier and the distribution diameter of the bolts. While contructing my new obs, I pondered this point. I wondered whether I should:
a) plonk the pier on the pad (no levelling but using a suitable filler material to properly couple the two),
b) suspend it on the bolts leaving an air gap (allows for re-levelling)
c) suspend on bolts but fill the gap to couple the pier to the pad (initial levelling only).
Here was my thought process:
I'm trying to make sure the resonant frequency of the system (if there is one) is high and damping is maximised
I have a 10" diam pier that would be suspended on three 3/4" (= pretty thick) stainless bolts on a 1" thick aluminium flange approximately 20mm above a 670mm tall concrete column 400mm in diameter. The distribution diameter of the bolts is 325mm. I.e. a pretty chunky setup for my equipment. The rigidity and resonant frequency will, almost by definition, be high for all three options given these parameters.
I have long since forgotten how to calculate resonant frequencies and bending moments for such a system let alone the contribution of the bolts!!! Anyway, I'm an empirical kind of guy! Maybe Peter can do the maths for me!!
I want to be able to level. If I adjust azimuth, I don't want to affect altitude & vice versa. Remember, even though it's a permanent setup, tweaking of polar alignment is a requirement over time (precession and maybe minor pier settling). Anyway, I'm a perpendicular kind of guy.
It's unlikely anyone will be jack-hammering anywhere near me while I'm imaging
There's a couple of hundred meters between me and the nearest road (with very light traffic)
I'm in a domed enclosure so wind is not much of a problem. And, more importantly, if the wind is strong enough to affect me, I’ll be inside sipping (polite talk for guzzling) wine.
I know I can couple the pier to the pad later if I really need to (but if I do, re-levelling will be a bugger of a job).
So, my conclusion was simple - stop pondering and suspend the b*&#$y thing on the levelling bolts and see if it works!!
My only tip if you go this way and you have a choice? Use no more than 3 heavier gauge bolts. The more bolts, the harder it is to level.
Result? So far so good. Simple observation through the eyepiece after a kick-the-pier test shows very fast damping and the system doesn't appear to ring. I'd describe it as rock solid. The acid test is when I start imaging again - if the clouds ever go away! Realistically though, I expect absolutely no problem.
One thing that I have pondered is when a mount has a memory of its last position when it was turned off (so it can do a power on re-start) does this algorith presume the mount is perfectly level? The SS2K powering my Vixen atlux seems to. When I re-start - even if it was off for 5 seconds or 5 weeks - pointing on the first star seems off by 3 arc minutes west. Makes me think the mount is slightly off level!
My approach was to do what what Peter suggested and simply go for the best level I could do without big bolts carring all the weight.
Anyway, I'm an empirical kind of guy! Maybe Peter can do the maths for me!! 
