Re: Pay Attention to Those Declination Top Plate Locking Knobs


M Hambrick
 

Thanks for the photos Jeff C.

In my younger days I used to carry my assembled 800 mount and 8-inch portable pier all at once, but no more. Everyone is talking about climate change, but what we should be talking about is gravitational constant change. What used to feel like it weighed 50 pounds when I was 38 now feels like it weighs over 100 pounds :>)

Shailesh - When I saw the photos from Jeff C they reminded me of a balancing issue that I had with my 180 EDT when I first got the mount. In Jeff's photo, the refractor in the rear with a 900 ? or 1200 ? mount on the 8-inch Astro-Physics portable pier looks very similar to what I started out with when I got my 1100 mount. You will also notice that his scope is attached to the mount on one of the A-P 18-inch Flat Plates (FP1800). I originally ordered my 1100 mount with one of these flat plates. I had to modify the plate by drilling some holes in it to match the hole pattern on my old 1992 vintage 8-inch rings, but when I was setting up everything inside the house to do the initial balancing, I could not get the scope to balance on the declination axis in the imaging mode with the camera attached. It was very heavy to the rear.

Rather than trying to drill additional holes in the flat plate, I solved the problem by purchasing one of the 16-inch dovetail saddle plates (DOVELM162) along with the 16-inch dovetail plate (SBD16). When I attached the scope to the mount using the DOVELM162 and SBD16 I was easily able to achieve balance in the declination axis by sliding the dovetail plate forward in the saddle plate.

The DOVELM162 and SBD16 have been one of the best investments I have made since purchasing the 1100 mount, and if you don't have them I highly recommend getting a set. I also purchased a couple of SBD12 dovetail plates to use with my smaller imaging scopes. The big advantage to this is that I can leave the DOVELM162 attached to the declination axis, and just attach whatever imaging scope I am using. Note that when I am setting up the 180 EDT, I first attach the SBD16 and attached rings without the 180 EDT to the dovetail saddle plate with the mount in the Park 2 position. Then, once the counterweights are attached I mount the 180 EDT into the rings. I have a set of portable stairs to facilitate this.

There is one other issue I should also mention if you have one of the A-P portable piers. I purchased my pier in 1992 for my 800 mount. It had three holes in the top for attaching the mount. The 1100 mount has 6 holes in the base. Although they told me that it was not necessary to do so, I drilled three additional holes in my pier to allow me to use all six screws. The 1100 mount base fits rather loosely into the 8-inch pier, and when the scopes, cameras, etc. as described in my earlier thread are attached to the mount, it places the center of gravity well outside (to the north) of the pier, and all that weight wants to tilt the mount towards the north. Even when the bolts attaching the mount base to the pier were tight I had several occasions where the mount tilted by about 1/16 inch after everything was attached and polar aligned using the RAPAS. To minimize the chance of this from happening I purchased some split Nord-Lock lock washers from McMaster-Carr (see below). These have been very effective at eliminating the tilting of the mount in the pier.

Mike

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