When I sketched out the initial design for my astronomy pier, I decided the mounting hole pattern on top should use the iOptron Tri-Pier hole pattern. There are Tri-Pier adpaters for lots of different telescope mounts, including my old CGEM and the Astro-Physics Mach 2 that I have on my dream sheet. That hole pattern let me buy an affordable and well designed adapter for my CGEM mount.

Unfortunately, there aren’t any ready-made adapters to mount a Losmandy G11 on an iOptron Tri-Pier. So, I designed my own. To lay everything out, I used the drawing of the bottom of the Losmandy G11/GM811/G8 pier adapter along with the specs of the Tri-Pier mounting holes. My idea whats to make just a simple plate that matched the outer diameter of the Losmandy pier adapter that would bolt to my pier and then have threaded holes to attach the Losmandy pier adapter on top. I 3d printed a test piece and it looked like it would work really well. Here’s what I came up with.

I sent the design to JLCPCB and had it CNC machined from 6061 aluminum and anodized gloss black. To save some money and speed up production, I didn’t have them tap the holes for the Losmandy pier adapter. Instead, I just sized the holes to tap them with the 1/4-20 threads they needed. A few weeks later, my adapter showed up in the mail.

The black finish matches the Losmandy pier adapter well, although the finish on my adapter looks pure black where the Losmandy G11 finish has a little hint of purple. Still, it looks like it belongs (you know, for the 1-2 people that ever visit my back yard).

Next step was tapping the holes for the Losmandy to bolt to. I only planned on using the inner 6 holes, but I started on one of the other holes in the adapter for practice. Good thing too – the crummy Harbor Freight tap set I used did a horrible job at cutting threads through the anodized finish and aluminum, even using cutting fluid. That tap ruined one of the holes. Figures. I bought a “real” tap and everything went smoothly after that.

Well, almost everything. I accidentally dropped my adapter and put a big ding in the corner when I was cleaning it in my shop. Oops. I filed it down and moved on.

I bolted my adapter to my pier using some low profile M10 stainless steel screws from McMaster.

After that, I placed my 3d printed power adapter holder and bolted down the Losmandy pier adapter using some stainless socket head screws, also from McMaster.

The pier & adapter were then ready for my G11 mount. Done!