Spacers and Adapters for the large Optec/DSI 3.5" x 24tpi threaded spec. Similar to the Astro-Physics 2.7" extension rings, adapters, and spacers our larger 3.5-inch standard provides a full 83mm of clear aperture.
Optec is a design and manufacturing firm specializing in electro-optical products used in astronomy, atmospheric science and microscopy. We are located in the town of Lowell, Michigan near the banks of the Grand River. Our company is small but we utilize state-of-the-art equipment and techniques in the design and manufacture of our products.