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IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
Baader T-2 Extension Tube- 7.5mm

Baader T-2 Extension Tube- 7.5mm

by Baader Planetarium
SKU BAA-1508155
$32.00 - $32.00
$32.00
$32.00 - $32.00
$32.00
Price Match Policy!
  • Adds 7.5mm of fixed optical path length
  • Part of the modular Baader T-2 Astro System
  • Standard T-2 (M42x0.75) internal and external threads
  • Precision machined for accurate spacing
  • Matte black anti-reflection finish
1 in stock
Qualifies for FREE Shipping in CONUS on orders over $350.
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Downloads
  • Warranty

  • Baader T-2 Extension Tube - 7.5mm

    The Baader T-2 Extension Tube adds a precise 7.5mm of spacing to any T-2 (M42x0.75) optical train, making it a fundamental component for achieving exact back focus with flatteners, reducers, and off-axis guiders. This component is essential for fine-tuning the critical distance between your camera sensor and corrective optics, where standard extension lengths are too coarse.

    The 7.5mm Increment: Precision in the Baader T-2 System

    Achieving the standard 55mm back focus often requires combining multiple spacers. The 7.5mm length is a critical "half-step" increment, allowing you to dial in spacing with sub-millimeter accuracy when combined with other T-2 components. It's the piece that bridges the gap between common 5mm or 10mm extensions, preventing you from being just a few millimeters short of perfect field correction.

    T-2 Thread Standard: M42 x 0.75 Integration

    Built on the universal T-2 thread standard (M42x0.75), this 7.5mm extension tube integrates seamlessly into the vast ecosystem of Baader Planetarium components and accessories from other manufacturers. Featuring male threads on one end and female threads on the other, it provides a rigid, non-flexing connection that maintains optical alignment far better than variable or helical extension systems. The interior is blackened to suppress stray light, preserving image contrast.

  • What is the main use for the Baader 7.5mm T-2 Extension Tube?

    The primary use for the Baader 7.5mm T-2 Extension Tube is to fine-tune the back focus distance in an imaging train. It provides a small, precise increment of spacing required by specific flatteners, reducers, or coma correctors to achieve sharp stars across the entire field of view.

    How does the 7.5mm tube help achieve the standard 55mm back focus for my coma corrector?

    Many imaging setups require a total of 55mm from the corrector's flange to the camera sensor. If your camera has a 17.5mm flange distance and you are using a 20mm and a 10mm extension, you will have 47.5mm of spacing. Adding this 7.5mm extension tube brings your total spacing to exactly 55mm, ensuring optimal performance from your corrector.

    Can I stack the 7.5mm Baader extension tube with other T-2 spacers?

    Yes. The Baader T-2 system is designed for modularity. You can stack the 7.5mm tube with any other T-2 threaded component, including other extension tubes, to build the exact length you need. The precision machining ensures the connections remain rigid and aligned.

    What are the threads on the Baader 7.5mm Extension Tube?

    This extension tube uses the standard T-2 thread, which is metrically defined as M42x0.75. It has male (external) threads on one side and female (internal) threads on the other, allowing it to be inserted between any two T-2 compatible accessories.

    Will this 7.5mm tube cause vignetting with my full-frame camera?

    The T-2 thread system has an internal diameter of approximately 41mm, which can cause some vignetting (darkening of the corners) on full-frame sensors (24x36mm). While the 7.5mm length adds minimal extra distance, the primary bottleneck is the T-2 diameter itself. For full-frame imaging, the larger M48 standard is generally recommended to avoid this issue.

    Why choose a fixed 7.5mm Baader tube over a variable extension?

    A fixed extension tube like this 7.5mm Baader tube provides superior rigidity and maintains perfect optical alignment. Variable extensions, while flexible, can introduce tilt or flex into the imaging train, which can degrade star shapes, especially with heavy cameras or long exposures.

  • Extension Length 7.5mm
    Threads T-2 (M42 x 0.75)
    System Baader Astro T-2 System
    Net weight (kg) 0.01
    Inner Diameter / Clear Aperture (mm) 38
    Outer Diameter 46
    Usage for eyepiece projection with sliding focuser

    • Baader T-2 Extension Tube (7.5mm)

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  • Baader Planetarium Warranty