Optec Inc. Optec-DSI 3.5x24tpi Extension Tube, 1/2” Length

• Joint Development Effort: A collaborative creation by Deep Sky Instruments and Optec, specifically for enhancing large aperture telescopes.
• Astro-Physics Compatibility: Complements the Astro-Physics 2.7-inch thread standard, expanding its application and use in astronomy.
• Clear Aperture Optimization: Designed to allow more light passage, reducing edge ray clipping and enhancing overall telescope performance.
• Robust Construction: Crafted from high-strength 6061 aluminum alloy, ensuring durability and reliability with a sleek black anodized finish.
• Female and Male Thread Design: Features versatile female threads on one end and male threads on the other, with knurled bases for easy attachment and detachment.
• Modular and Stackable Extensions: The 1/2” extension tube can be combined and stacked with others in the set, offering flexible extension solutions.
• Precision Increments for Focal Lengths: Ideally suited for fixed focal length telescopes, providing necessary extensions in precise 1/4" (6.35mm) increments.
• Minimized Internal Reflections: Equipped with anti-reflection threading and internal baffles to significantly reduce unwanted internal light reflections.
• Non-Reflective Interior Coating: All internal surfaces are coated with an ultra-flat black paint, optimizing optical performance by minimizing internal reflections.
• Enhanced Telescope Functionality: Suitable for astronomers and astrophotographers seeking to improve their telescope's capabilities with quality extension tubes.

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.