Re: Potential Issue: Mount Shifting on Pier After Setup

Donald Rudny

Hi Mike,

Just my two cents, but I think your problem is due mainly to a loose fit on your vintage pier.  There is probably some clearance between the pier inside diameter and mount OD that allows for some cocking with the clearance between the bolt hole on the pier and bolt thread on the mount.  You can crank all you want on the bolts, but you are relying on the clamp load to prevent slippage and subsequent cocking of the mount in the pier bore.  

I think your best solution is to mount an AP flat surface adapter and flat pier plate to your pier as George suggested.  They sell the combo as 119FSA-FP.  The trick will be to the method of mounting this to your pier so you don’t have the same problem.  I think the best would be to drill a 3/4” hole in the center of the flat pier plate and run a threaded rod to a bar at the bottom of the tube and clamp the pier plate to the pier tube as well as using the six bolts on the diameter.  Then you have a rock for your mount.  The AP flat surface adapter is precisely machined so the 1100 mount base will not cock in the bore.  There is also very little clearance in the bolt holes on the diameter.  Roland makes some extremely well designed and machined components.  I have these pier plate too, and the precise fit amazes me.  I think your problem is your clearance on your “vintage” pier.

Hope this helps.


Don Rudny

On Nov 7, 2018, at 2:55 PM, mike.hambrick@... [ap-gto] <ap-gto@...> wrote:


Thanks for the comments George. 

To your points: 

I will have to read my 1100GTO manual again about when to polar align. After l I bought my 1100 mount, I was still using the polar alignment procedure that I used for my old 800 mount, and it was not really designed to be able to adjust the altitude or azimuth after the scope and counterweights were attached. The adjustment mechanisms on the 1100 mount are much more robust, and being able to attach everything before polar aligning will make a big improvement to my setup time. 

I don't have a permanent pier, but I never set up on grass or dirt either. I have 4X6 treated wood posts buried 18 inches deep into my back yard that have the same footprint as the pier legs. They are level and are immovable. They provide a very stable base for my mount. When I set up this way, the polar alignment is already pretty close. The altitude is almost always spot-on, and I usually only need to make a minor azimuth adjustment. 

Using longer bolts makes sense. I will do this immediately. The original bolts were 3/4 inch. I will use the longest bolts I can without bottoming out. 

I don't think the mount holes in my pier are oblong. The original pier that came with my 800 mount had only three holes. They were at least 11/32 inch diameter, so there has always been a lot of extra play. I had to drill three additional holes in the pier so I could use all six mounting holes on the 1100 mount. 

I really like the idea of a flat pier plate and flat surface adapter. I will definitely consider these, but I don't see the M9010A on the web site.

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