Pulsar pier on a concrete pad - stability

[Elliot_H]

Hello folks - my first post on SGL!

15 years ago I had a 12" reflector, and had started to have fun... when life got in the way and I moved - to a place that wasn't suitable for a back-yard scope/obs.

I'm now retiring and have moved to a more astro-friendly house.
Am setting-up a new instrument... in a small courtyard. It will be remotely-controlled.
It's a RASA 11" on a CGX mount, and I've splashed out on the not-so-cheap Pulsar steel pier.

I have built a concrete pad on top of existing (uneven, sloping) concrete.
Having got Pulsar's pier fitting-kit, the 4 bolts are now locked into the pad/existing-base.

However, the surface of my pad is not as flat as I'd hoped. I put too much faith in gravity!
In fact, when I put the pier into place on the bolts... it rocks back and forth.
On one side of the pier - there is a gap of about 3 mm.

Question: 
Do you think would it be OK to put washers between pad & pier... ie under the 2 "gappy" bolts?
Or should I use a levelling compound to achieve a properly flat (and horizontal) surface?
Not sure how strong the latter really is - under compression...
I believe Pulsar recommend torqueing the nuts very tightly.

As you can imagine, I will be doing astro-photography.
I have had some success with the RASA just on tripod, but obviously I want the pier as stable as possible.

Cheers, Elliot
 

[old_eyes]

The short answer is yes. I have a couple of washers on one bolt where the concrete sagged a bit. The result is rock solid when firmly tightened down. My Pulsar pier has an adjustable top plate so once everything was solid I used that to level the mount. No problems for the last 18 months. With a wide field scope like a RASA you should have no problems with the pier.

[souls33k3r]

First of all, welcome back mate. 

Now the answer to your main question, yes it is alright to put washer between the pad and the pier because I have done it myself. My concrete pad was level enough and was rock solid but the OCD (even though it really didn't matter in my case) in my wanted the pier to be levelled. So I went ahead and placed 2-3 washers on 3 sides and I was good to go. The darn thing never moved. 

Hope this helps. 

[tomato]

I think this will be fine, my pier has 8 machined spacers under it to get the flange flush with the false floor in the observatory and it ain’t moving anywhere when bolted down, even with ~100 kg all up load riding on it.

[Elliot_H]

Thank you - to all 3 repliers.

I'm getting some M16 2mm-thick steel washers tomorrow and I will experiment with them.
I can see having the top of the pier perfectly horizontal is desirable.. but it's not essential with an equatorial mount, right?

I've enjoyed watching these 2 videos on Pulsar piers.
Anyone know what Robert Dalby is up to these days? He is very thorough in his responses to comments + criticisms!
Sadly the other chap Ralph Bell has passed away I believe...