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Optec DSI 3.5" Extension Tube Set - 5 Pieces

Optec DSI 3.5" Extension Tube Set - 5 Pieces

by Optec
SKU OPC-19890
CA$350.00 - CA$350.00
CA$350.00
CA$350.00 - CA$350.00
CA$350.00
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  • Five-piece set with 1/2, 3/4, 1, 1-1/2, and 3-inch lengths
  • Creates any spacing from 0.5 to 6.25 inches in 1/4-inch steps
  • Total combined extension of 6.75 inches (171.45 mm)
  • Standard DSI 3.5-inch x 24 TPI male and female threads
  • 6061-T6 aluminum with a black anodized finish
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • Optec DSI 3.5" Extension Tube Set - 5 Pieces

    The Optec DSI 3.5" Extension Tube Set provides a complete, modular solution for achieving precise back focus in large-format imaging systems. This five-piece set, made of 6061-T6 aluminum, allows you to create spacing from 12.7 mm (0.5 in) up to 171.45 mm (6.75 in) using combinations of the included tubes. With standard DSI 3.5-inch x 24 TPI threads, this kit enables you to dial in the exact distance required by your camera, off-axis guider, and corrector in 6.35 mm (1/4 in) increments.

    A 0.5" to 6.75" Range in 1/4" Increments

    The set includes five individual extension tubes with lengths of 1/2, 3/4, 1, 1-1/2, and 3 inches. By stacking these tubes, you can achieve any required spacing between 0.5 inches and 6.25 inches in precise 1/4-inch steps. Combining all five tubes yields a maximum total extension of 6.75 inches (171.45 mm).

    Self-Centering DSI 3.5" x 24 TPI Threads

    Built around the large-format DSI 3.5-inch x 24 TPI thread standard, the tubes are made of 6061-T6 aluminum, black anodized. Optec's drawings show a 30-degree contact surface that makes the set self-centering when stacked.

    • Secure Grip: A knurled base on each extension provides a firm grip for easy attachment and removal.
    • Stackable Design: Each tube features male threads on one end and female on the other, allowing them to be combined in any order to build up the required length.

    Baffled and Threaded for Maximum Contrast

    To protect your images from stray light, the extensions have anti-reflection threads inside, and the longest 3-inch tube also has internal baffles, which help minimize internal reflections.

  • What is the main purpose of the Optec DSI 3.5" Extension Tube Set?

    The Optec DSI 3.5" Extension Tube Set is used to achieve the correct back focus distance between a telescope's corrector or focuser and the imaging camera sensor. This five-piece set allows you to build a wide range of precise lengths from 0.5 to 6.75 inches to match the requirements of your specific optical train, which might include cameras, filter wheels, and off-axis guiders.

    How would I use the Optec DSI 3.5" set to achieve 2.25 inches of spacing?

    To achieve 2.25 inches of spacing, you would combine two tubes from the set. Stacking the 1-1/2 inch tube and the 3/4 inch tube together (1.5 + 0.75) gives you exactly 2.25 inches. The set is designed to create any length from 0.5" to 6.25" in 1/4" increments by combining different tubes.

    What imaging systems use the DSI 3.5" x 24 tpi thread standard?

    The DSI 3.5-inch x 24 TPI (threads per inch) standard was developed by Deep Sky Instruments and Optec for large-format imaging systems that require a wide, unvignetted light path. Optec uses it, for example, on the camera side of the Gemini Focusing Rotator through the #19830 adapter.

    Are the extension tubes in the Optec set designed to prevent internal reflections?

    Yes. All tubes in the Optec DSI 3.5" set feature internal anti-reflection threading to trap stray light. The largest 3-inch extension also includes internal baffles , which help minimize internal reflections.

    Can I stack all five tubes from the Optec set together?

    Yes, all five tubes can be stacked together to achieve the maximum possible extension of 6.75 inches (171.45 mm). Optec's drawings show a self-centering contact surface on each tube; when stacking multiple components, it is important to ensure each connection is firmly tightened to maintain rigidity in the imaging train.

    What are the individual lengths included in the Optec DSI 3.5" set?

    The five-piece set includes the following extension tube lengths:

    • 1/2 inch (12.7 mm)
    • 3/4 inch (19.05 mm)
    • 1 inch (25.4 mm)
    • 1-1/2 inches (38.1 mm)
    • 3 inches (76.2 mm)
  • Thread DSI 3.5 in x 24 tpi, female on one end, male on the other
    Included Lengths 12.7, 19.05, 25.4, 38.1 and 76.2 mm (1/2, 3/4, 1, 1-1/2 and 3 in)
    Possible Combinations 12.7 to 158.75 mm (0.5 to 6.25 in) in 6.35 mm (1/4 in) steps, plus 171.45 mm (6.75 in) with all five
    Material 6061-T6 aluminium, black anodized
    Optical Length 1/2 in: 12.7 mm; 3/4 in: 19.05 mm; 1 in: 25.4 mm; 1-1/2 in: 38.1 mm; 3 in: 76.2 mm

    • DSI 3.5 in extension, 1/2 in

      × 1

    • DSI 3.5 in extension, 3/4 in

      × 1

    • DSI 3.5 in extension, 1 in

      × 1

    • DSI 3.5 in extension, 1-1/2 in

      × 1

    • DSI 3.5 in extension, 3 in

      × 1

  • Optec 1-Year Warranty