Ortho 2x Barlow lens

Barlow lenses and traditional extenders increase focal length but tend to degrade the image.

With its Ortho 2x Barlow lens, Takahashi offers a focal extender that aims to retain as many of the properties of the objective with which it is associated as possible. To design its eyepieces and Barlow lens, Takahashi works on the entire optical chain, starting with an aberration-free telescope (generally, the reference is the apochromatic triplet of the TOA refractor) and ending with the eye or with the sensor; the aim being to add no additional aberration, or even to correct certain defects in the objective. In fact, the combination of the Barlow lens with TPL series eyepieces produces a better quality image, whether at the center of the field or at the periphery, than when the Barlow is not used. At the center, the Barlow lens even cancels out the very low residual chromatic aberration of the TOA objective. The photographic performance of the Barlow Ortho 2x lens is clearly greater than the old model, both in terms of chromatism and coma.

In addition to the classical 1.25" (31.75 mm) female barrel, a male T thread (M42x0.75) has been added. This allows direct screwing of cameras or DSLRs (with the addition of a T ring)).

The magnification ratio of the Takahashi Ortho 2x Barlow lens varies as a function of the distance to the lens to the formula m = 2 + 0.0121 x b, where m is the magnification and b is the distance between the end of the T thread and the surface of the sensor (or entrance diaphragm in the case of an eyepiece).

For a ZWO planetary camera with a backfocus length of 17.5 mm, the value of b is 12.5 mm (the T-thread is 5 mm long). So, according to the formula above, the magnification is 2.15.

Main characteristics

Magnification