General

I noticed a bit of motion on my Astro-Tech AT60ED when everything was put together. I don't know how much affect it has on imaging but I didn't like it. This isn't the strongest of designs, but it should be super good enough as long as you're using it in conjunction with the original mount. Typical screw-into-plastic style assembly. I printed with PLA, PETG should be fine assuming the holes end up the same size as in PLA. Print file included for settings and estimated time reference, ymmv. You will not be able to collapse the dew shield while this ring is installed, at least not all the way. 

Printing

• No supports should be needed
• Should be oriented properly on load (only tested with Prusa)
• I used 15% infill but you may wish to use more
• 3 perimeters (minimum for 0.1mm layer thickness)

Hardware

• 4x M3x12mm socket-headed cap screws
• 2x M5x12mm socket-headed cap screws
• 2x M5 flat washers

Assembly

The bottom should be able to slide between the scope and the dovetail plate while imaging train is still assembled. It may be particular to this dovetail plate, but you will need ~30mm in front of the scope's original mount, and you will need two holes ~20mm apart on center. They will likely be ¼-20 sized holes but the hole on this printed part is for M5 as the bulk of fasteners I have are metric. I recommend M5 flat washers to support the size difference in holes. See pictures for visual. Top half of the ring should be self-explanatory, but be gentle when tightening as you could easily strip the bottom holes, and not much clamping force is required by the ring. Once the ring is making full contact all the way around the scope and the screws become snug, you're set. Check by wriggling the ring back and forth and checking for any looseness. You should have ~2.1mm gap on both sides between the top and bottom halves of the ring. Again, see photos for visual.

Specs

For those using it for other purposes:

• 15mm overall thickness
• 76.15mm ID
• 7mm strap thickness
• 28.5mm between ID and flat base (between the scope and dovetail plate)
• 35mm wide flat base
• 20mm between centers on the flat base holes
• 8mm hole depth on flat base

Footnote

Let me know if I got something horribly wrong, I don't know what I'm doing either.