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David Astro M42 Extension Tube - 3mm

by David Astro
SKU DAV-T2-EXT-3
CA$15.00 - CA$15.00
CA$15.00
CA$15.00 - CA$15.00
CA$15.00
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  • Adds 3mm of spacing to an imaging train
  • M42x0.75 T2 thread
  • Helps set the back focus of a flattener, reducer or corrector
  • Can be stacked with other M42 extension tubes
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  • Description
  • FAQ
  • Specifications
  • In the Box

  • David Astro M42 Extension Tube - 3mm

    The David Astro M42 Extension Tube - 3mm adds a fixed 3mm of length to an imaging train that uses the M42x0.75 T-thread (T2). Use it to place your camera sensor at the distance a field flattener, reducer or corrector needs.

    Fixed 3mm Spacing for Correct Back Focus

    Field flatteners, reducers and coma correctors give their sharpest stars only when the camera sensor sits at a set distance behind them, the back focus. This tube closes a 3mm gap in that distance. Several tubes can be stacked to build the total spacing your setup needs.

    The M42x0.75 T-Thread

    M42x0.75 means a 42mm metric thread with a 0.75mm pitch. It is the T-thread, or T2, used by many cameras, T-rings, filter wheels, off-axis guiders and adapters, so the tube fits into the T2 part of most imaging trains.

  • What is the David Astro M42 Extension Tube - 3mm used for?

    It adds a fixed 3mm of spacing between the components of an imaging train, most often to reach the back focus distance required by a field flattener, reducer or corrector.

    Can I stack the David Astro M42 Extension Tube - 3mm with other M42 extension tubes?

    Yes. Extension tubes are made to be combined. Add this 3mm tube to other M42 tubes to build the total spacing you need.

    What does M42x0.75 mean on the David Astro M42 Extension Tube - 3mm?

    M42x0.75 is a 42mm metric thread with a 0.75mm pitch. It is the T-thread, also called T2, widely used for astrophotography accessories.

    How do I know if I need a 3mm extension tube?

    Add up the spacing of your camera and adapters and compare it with the back focus your corrector requires. If the gap is 3mm, or 3mm is one of the pieces that makes up the gap, this tube fills it.

    What happens if the back focus spacing is wrong?

    Correctors are designed to work at one distance from the sensor. If the spacing is off, stars near the corners of the image become elongated or distorted.

  • Brand David Astro
    SKU DAV-T2-EXT-3
    Thread M42x0.75 (T2 / T-thread)
    Length 3mm

    • David Astro M42 Extension Tube - 3mm

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