Barlow lens


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Barlow lens

(bar -loh) An achromatic diverging lens (see achromatic lens) placed behind the eyepiece of a telescope, just inside the primary focal plane, in order to increase the effective focal length of the objective or primary mirror. This increases the magnification of the telescope so that a long-focus eyepiece may be used to give the higher powers needed to separate optical doubles, or for planetary observation under the best seeing conditions.

Barlow lens

[′bär‚lō ‚lenz]
(optics)
A lens with one plane surface and one concave surface that is placed between the objective and eyepiece of a telescope to decrease the convergence of the beam from the objective and thereby increase the effective focal length.
References in periodicals archive ?
5x barlow lens giving a focal length of 3 000 mm, mounted on Skywatcher HEQ5 GOTO equatorial mount and a Meade Astrometric eyepiece.
An excellent choice for any burgeoning explorer, it's equipped with a rotating eyepiece turret holding 25-, 15-, and 6-mm eyepieces, along with a removable 18-mm image erecting eyepiece and a power-doubling Barlow lens, giving eight magnification powers to select from.
I was able to see Mars clearly through an eight-inch reflector, using a three times Barlow lens and a 20 mm eyepiece.
4" from the fainter component I can easily split it with my 8-inch telescope at 200-power by using a 2x Barlow lens and a 10mm Plossl eyepiece.
5X erecting eyepiece, a 2X Barlow lens and 10X reflexing finderscope.