| This black-anodized Astro-Tech dovetail adapter clamps onto a Losmandy-style “D-plate” dovetail plate. The adapter lets you install tube rings, photoguide rings, or other accessories on a wide Losmandy-style dovetail plate that is mounted piggyback on a larger optical tube. This lets you piggyback a second scope or photoguide scope on your main scope.
A single hand-tighten knob clamps the Astro-Tech adapter firmly in place on a Losmandy-style “D-plate” dovetail, but allows the adapter to be quickly repositioned along the dovetail so you can balance or change accessories as needed with no tools required. A three-legged lever on the knob shaft lets you apply extra pressure to clamp very heavy loads when wearing gloves or mittens. The lever also makes it easier to loosen the clamp should cold weather cause the metal to contract and the adapter to bind on the dovetail.
A series of seven unthreaded 6.9mm diameter mounting holes are drilled into the adapter in the pattern shown in the photos. The pattern and spacing of the mounting holes is shown in the engineering drawing in the feature image below. These holes allow you to use 1/4”-20 or metric bolts to mount virtually any finderscope ring, off-axis photoguide ring, ball-head camera mount, etc., on the adapter.
The holes are countersunk on the underside of the adapter so that the mounting bolts holding the accessories will not interfere with the dovetail plate. The adapter measures 4.45” wide when the clamp is fully tightened. It is 2.5” long fore and aft and 0.75” deep. The height from the top of the dovetail plate to the top of the adapter is 0.5”. The adapter weighs 10.4 oz. It is hard-anodized black for long life and durability. | 
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