Optec Inc. Optec-DSI 3.5x24tpi Extension Tube, ¾” Length

• Collaborative Design: Developed in partnership by Deep Sky Instruments and Optec, tailored for large aperture telescopes.
• Astro-Physics Standard Compatibility: Enhances the widely recognized AP 2.7-inch thread standard, extending its applications in astronomy.
• Optimal Light Passage: Designed to facilitate maximum light throughput, addressing limitations of the AP2.7 spacers in edge ray clipping.
• Durable Material Construction: Crafted from high-strength 6061 aluminum alloy, ensuring long-lasting reliability with a black anodized finish for added durability.
• Versatile Thread Configuration: Features female threads on one end and male threads on the other, with knurled bases for easy and secure attachment.
• Stackable Extensions: Allows for combining and stacking with other extensions in the set, providing adaptable solutions for telescope extension needs.
• Precise Incremental Adjustments: Ideal for fixed focal length telescopes, offering essential extensions in 1/4" (6.35mm) increments for precision adjustments.
• Internal Reflection Reduction: Equipped with anti-reflective threading and internal baffles to minimize internal light reflections and enhance optical performance.
• Ultra-Flat Black Interior Coating: All internal surfaces are coated with a non-reflective, ultra-flat black paint, optimizing the telescope's optical efficiency.
• Comprehensive Spacer Options: Part of a set that includes varying lengths (including ½”, ¾”, 1", 1-1/2", and 3") to cover a wide range of spacer combination needs, ensuring compatibility with various telescope setups.

Specifications

• Overall Height: Varies
• Clear Aperture: 3.25" (82.5mm)
• Weight: 1.0 oz. (30 g)
• Back-focus Usage: 0.50" (12.7mm)
• Drawing
• Table for spacer combinations.