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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.
Baader Planetarium M48 Extension Tube – 7.5 mm
Baader Planetarium M48 Extension Tube – 7.5 mm
Baader Planetarium M48 Extension Tube – 7.5 mm

Baader Planetarium M48 Extension Tube – 7.5 mm

by Baader Planetarium
SKU BAA-2958607
$36.00 - $36.00
$36.00
$36.00 - $36.00
$36.00
Price Match Policy!
  • Adds 7.5 mm of optical path length
  • Standard M48 x 0.75 female and male threads
  • Precision-machined for a rigid, tilt-free connection
  • Matte black interior to prevent internal reflections
2 in stock
Qualifies for FREE Shipping in CONUS on orders over $350.
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Downloads
  • Warranty

  • M48 Extension Tube – 7.5 mm

    The Baader M48 Extension Tube adds exactly 7.5 mm of length to your imaging train, providing a critical tool for achieving precise back focus with M48-threaded accessories. This component is essential for fine-tuning the distance between field flatteners, coma correctors, and your camera sensor.

    Fine-Tune Your Imaging Train with 7.5 mm of Extension

    Optical correctors like field flatteners and reducers demand exact spacing to deliver sharp stars across the entire frame. This 7.5 mm extension tube provides a crucial intermediate step when standard 5 mm or 10 mm extensions are too short or too long. It allows you to dial in the perfect distance with sub-millimeter accuracy by combining it with other spacers.

    • Eliminate Star Elongation: Achieve the exact back focus required by your optics to correct for coma and field curvature, turning elongated edge-of-field stars into sharp points.
    • Bridge Small Gaps: Use this 7.5 mm tube to fill small, calculated gaps in your optical train, especially when accommodating off-axis guiders or filter wheels.
    • Stackable Design: Combine with other M48 extensions and tuning rings to build up any custom spacing distance your imaging setup requires.

    Rigid M48 Connection for Modern Cameras

    This extension tube features standard M48 x 0.75 threads for a secure, non-flexing fit between your components. Unlike older T-2 connections, the larger M48 format is better suited for full-frame sensors, minimizing the risk of vignetting. The tube is engineered to integrate with modern cameras and accessories that often have very specific and minimal spacing tolerances.

  • What is the primary use for the Baader 7.5 mm M48 Extension Tube?

    Its primary use is for back focus adjustment in an astrophotography imaging train. Optical correctors (like field flatteners or coma correctors) require a precise distance to the camera sensor to work correctly. This 7.5 mm tube helps you achieve that exact distance when other components don't add up perfectly.

    How do I know if I need a 7.5 mm M48 tube for my setup?

    You need to calculate the total back focus of your current imaging train. Start with the required back focus of your flattener/reducer (e.g., 55 mm). Then, add up the optical path length of every component after it: your off-axis guider, filter wheel, and the camera's sensor flange distance. If the total is, for example, 47.5 mm, this 7.5 mm extension tube will provide the exact spacing needed to reach 55 mm.

    Can I stack this 7.5 mm M48 Extension Tube with other extensions?

    Yes, absolutely. These tubes are designed to be stacked to create custom lengths. For maximum rigidity, it is always best to use a single extension of the correct length if possible. However, stacking a few high-quality tubes like this Baader extension is a common and effective practice for achieving precise spacing.

    Will adding the M48 Extension Tube – 7.5 mm cause vignetting?

    Because it uses the large M48 (2-inch) thread standard, this extension tube is designed to prevent vignetting on sensors up to full-frame (35mm) format. Vignetting is more likely to be caused by other components in the optical train, such as a smaller T-2 (M42) threaded item, rather than this M48 extension.

    How can the 7.5 mm M48 tube help with a Baader MPCC Mark III on a Newtonian?

    The Baader MPCC Mark III coma corrector requires a nominal back focus of 55 mm. If you are using a DSLR with a standard 44 mm flange distance and a 10 mm T-ring, you are already at 54 mm. A 1 mm M48 tuning ring would be ideal. However, if you are using a dedicated astronomy camera with a shorter back focus, like a ZWO camera with a 17.5 mm flange distance, you will need to add spacers. This 7.5 mm tube can be part of the combination of extensions needed to build up the remaining 37.5 mm distance.

    I have a Celestron EdgeHD with a 0.7x reducer. How would this 7.5 mm M48 tube be useful?

    The Celestron 0.7x reducer for EdgeHD scopes requires a very generous 146 mm of back focus. This distance must accommodate an off-axis guider, filter wheel, and camera. The 7.5 mm M48 tube is perfect for the final fine-tuning stage. After you've assembled your main components and larger extensions, you can use this smaller tube to precisely dial in the last few millimeters to hit that 146 mm target perfectly.

  • Optical Length 7.5 mm
    Inner/Outer Thread M48 (2")

    • M48 Extension Tube – 7.5 mm

      × 1

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