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Takahashi Ortho extender 4x - 1

Takahashi Ortho extender 4x

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Takahashi excellent optical quality ortho extender (barlow) available in 2x and 4x magnification.

Do you have a question about this product?

The Ortho Extender is an amplifying lens that enlarges the image by extending the focal length while maintaining almost the same image quality as the native focal length. If you install it in an optical system such as the TOA series that is well corrected for central aberration, one can obtain an enlarged image with optimal image quality.

If used with an optical system that has peripheral coma, the optimized image circle will become narrower but central image quality is still maintained.

The Ortho Extender 2X, with a magnification ratio of two times is suitable for photographing the entire moon and small astronomical objects such as small galaxies and planetary nebulas. The recommended optical system is a telescope with as little aberration as possible and an f/ratio of f/5 or slower.

The Ortho Extender 4X, which has a magnification ratio of four times, is intended to be attached to telescopes with f/ratios from f/8 to f/10, and is used for close-up photography of planets, craters on the moon, etc.

Although eyepieces can be used for magnified photography using afocal or projection techniques, they are designed for visual applications. Our Ortho Extenders, which are optically designed primarily for photography, are better corrected in terms of both central and peripheral aberrations.

If used with the TOA series, it will be the perfect combination to magnify the TOA image without chromatic aberration. The rear end of the main body has a 31.7mm (1.25 inch) diameter sleeve insertion port and an M42 with P0.75 T-ring screw, allowing you to attach a CMOS camera or other camera mount.

Both Takahashi Ortho Extender 2X and Takahashi Ortho Extender 4X consist of the main body, extension tube (large), extension tube (small) and M42-31.7AD.

Magification Ratio

To connect the Ortho Extender to your Takahashi telescope, first, remove the eyepiece adapter connection ring from the M43 thread of the 50.8 sleeve visual adapter (FS-60CB), visual adapter (CCA-250), etc. Second, thread the Ortho Extender 2X or 4X in to the 50.8 sleeve/visual adapter (FS-60CB), visual adapter (CCA-250), etc. The magnification ratio when using an Ortho Extender is calculated using the following formula:

  • Ortho Extender 2X: Magnification = 1.27 + 0.0126 * b
  • Ortho Extender 4X: Magnification = 2.02 + 0.0258 * b

b: Back Focus (mm) = Extension Tube (large) + Extension Tube (small) + Distance from M42-31.7AD’s end-edge without threading area to the imaging plane or principal point of the eyepiece.


  • Lens configuration: 1 group 2 elements (Ortho Extender 2X) or 2 groups 4 elements (Ortho Extender 4X)
  • Magnification: 2X (Ortho Extender 2X) or 4X (Ortho Extender 4X)
  • Image circle : 20~30mm (Diameter of Optimized Image Circle)
  • OTA side installation size: M43 P0.75
  • End-side installation size: M42 P0.75/31.7mm (1.25 inch) Sleeve Port
  • Maximum diameter x total length (excluding protrusions): 46mm x 103mm (Ortho Extender 2X) or 46mm x 125mm (Ortho Extender 4X)
  • Mass: 190g (Ortho Extender 2X) or 240g (Ortho Extender 2X)
  • The recommended back focus considering the aberration tolerances of the Ortho Extender is:
    • Ortho Extender 2X: 45~92mm with magnification rate: 1.9-2.49x
    • Ortho Extender 4 X: 60~92mm with magnification rate: 3.7~4.53x
Magnification Factor



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Takahashi Ortho extender 4x

Takahashi Ortho extender 4x

Takahashi excellent optical quality ortho extender (barlow) available in 2x and 4x magnification.

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