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Baader M68 Extension Tube - 7.5mm
Baader M68 Extension Tube - 7.5mm

Baader M68 Extension Tube - 7.5mm

by Baader Planetarium
SKU BAA-2458212
CA$69.00 - CA$69.00
CA$69.00
CA$69.00 - CA$69.00
CA$69.00
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  • Provides 7.5mm of fixed extension
  • M68 x 1mm female and male threads
  • Maintains a large, unvignetted clear aperture
  • Precision machined for accurate spacing
  • Matte black anti-reflection finish
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • Baader M68 Extension Tube - 7.5mm

    The Baader M68 Extension Tube provides exactly 7.5mm of fixed, non-flexing spacing for imaging trains built around the robust M68 thread standard. It is a critical component for achieving the precise back focus required by field flatteners, reducers, and coma correctors, especially in setups with large sensors and heavy accessories where rigidity is paramount.

    The Baader M68 System: A Rigid, Wide-Aperture Standard

    The M68 threaded system is Baader's professional standard for connecting heavy cameras, large filter wheels, and off-axis guiders without the risk of tilt or flexure common in smaller M48 or T-2 systems. This extension tube maintains the system's large clear aperture, ensuring that the light cone from the telescope is not vignetted before it reaches the sensor. This is especially important for full-frame sensors and fast optical systems.

    Unlike variable or helical spacers, a fixed extension tube like this one offers absolute rigidity. Once threaded into place, it becomes a solid part of your optical train, eliminating a potential source of mechanical error that can compromise image sharpness.

    Achieving Critical Back Focus with 7.5mm Spacing

    Correctors and reducers demand a specific distance to the sensor, typically 55mm, to deliver a flat, sharp field. The 7.5mm length of this Baader tube is a specific increment designed to close the gap when your other components (camera body, filter wheel, OAG) don't add up to the required total. It allows you to fine-tune your spacing with a solid, reliable component rather than stacking thin, less stable shims.

    • Solid Construction: Machined from aluminum with a black anodized finish to prevent reflections inside the imaging train.
    • Precise Length: Provides a known, repeatable 7.5mm of spacing for calculating your back focus distance accurately.
    • M68 Threads: Features one male and one female M68 x 1mm thread for direct integration into the Baader M68 component ecosystem.

  • What is the primary use for the Baader M68 7.5mm Extension Tube?

    Its primary purpose is to add a precise 7.5mm of spacing in an astrophotography imaging train to achieve the exact back focus distance required by a field flattener, reducer, or coma corrector. It is used within the Baader M68 threaded system for a rigid, flex-free connection.

    My flattener needs 55mm of back focus, but my camera and OAG total 47mm. Is this Baader 7.5mm tube the right part?

    Almost. You have a gap of 8mm (55mm - 47mm). This 7.5mm tube will get you very close, leaving you only 0.5mm short. You would typically use this tube in combination with a 0.5mm M68 spacer shim to achieve the perfect 8mm distance. Using a solid tube for the majority of the distance ensures maximum rigidity.

    Why should I use a Baader M68 extension tube instead of more common M48 (2-inch filter thread) spacers?

    The M68 system offers a significantly larger clear aperture than M48, preventing vignetting on full-frame and larger sensors. It also provides a more robust and rigid threaded connection, which is critical for preventing tilt and flex when using heavy cameras, filter wheels, and other accessories.

    What is the thread pitch on the Baader M68 7.5mm Extension Tube?

    This extension tube uses the standard M68 x 1mm thread pitch. It has male threads on one side and female threads on the other, allowing it to be inserted between any other two M68 components.

    Will this 7.5mm extension tube degrade my image quality?

    No. An extension tube is a passive optical-mechanical component. It contains no lenses. Its sole function is to provide spacing. As long as the interior is properly blackened to prevent reflections, like this Baader tube, it will have no negative impact on image quality.

    Can I stack this Baader 7.5mm tube with other M68 extension tubes?

    Yes. The Baader M68 system is designed to be modular. You can thread multiple extension tubes together to create any custom length you require. For example, stacking this 7.5mm tube with a 10mm tube would give you a rigid 17.5mm extension.

  • Thread Type M68 x 1mm (Male and Female)
    Extension Length 7.5mm
    System Baader M68 System
    Net weight (kg) 0.03
    Compatible Brands Baader Planetarium, Zeiss
    Inner Diameter / Clear Aperture (mm) 62
    Outer Diameter 76
    Usage serves as additional focus distance for eyepiece projection or FFC
    Inner Connection (eyepiece/-camera-sided) M68 x 1
    Outer Connection (lens sided) M68 x 1

    • Baader M68 Extension Tube - 7.5mm

      × 1

  • Baader Planetarium Warranty