The Tele Vue Dioptrx Astigmatism Correcting Lens - 0.25 Diopter is a special corrector lens, that has the ability to be attached and locked onto the tops of over 20 Tele Vue eyepieces with long eye relief. The Dioptrx series of lenses are used specifically to compensate for your eye's astigmatism. This gives you the sharpest full-field observing possible.

Tele Vue Dioptrx models are available in 0.25 diopter steps, from 0.25 up to 3.5 diopters, and are rotatable for tuning to the best orientation. A series of engraved letters on the barrel helps to monitor their orientation. Simply choose the Dioptrx model that matches your eyeglass prescription for astigmatism.

To overcome the common vision limitation called astigmatism, which the majority of people have, Tele Vue has developed a corrector which fits directly onto the eyepiece. Previously, the only way to correct for this was by wearing eyeglasses. That is, until now! Tele Vue Dioptrx Astigmatism Correcting Lenses extract the maximum visual performance you can get from your telescope and eyepieces. All the Dioptrx lenses are multi-coated glass in anodized aluminum housings, with rubber eyeguards for comfort.

• 31 mm Nagler type 5

• 26 mm Nagler type 5

• 41 mm Panoptic

• 35 mm Panoptic

• 27 mm Panoptic

• 22 mm Panoptic

• 55 mm Plossl

• 40 mm Plossl

• 32 mm Plossl

• All Radians (18 mm thru 3 mm)

• All Nagler type 4 (22 mm, 17 mm, 12 mm)

• First, look at your eyeglass prescription for any astigmatism in your dominant eye, which is the one you primarily use for observing

• Second, note the longer focal length of your Tele Vue eyepieces that apply, and obtain a Dioptrx lens for that value of astigmatism on your prescription.

Observers do not need eyeglasses to compensate for near- or far-sightedness since telescopes can focus out these limitations. Furthermore, other eyeglass characteristics, such as bi-focal, tri-focal, or vari-focal (progressive) designs are severely detrimental when trying to view a large field at infinity. In the past, it was recommended to get a special pair of "astronomy-only" eyeglasses that only has your astigmatism correction and multi-coatings. It is suggested to follow a procedure to determine at what size exit pupil your astigmatism needs correction since at higher powers (with their smaller exit pupils) eyeglasses may not even be necessary. Note: large exit pupils are typical for viewing with large aperture instruments, such as Dobsonians, and for wide angle viewing with small refractors.

Tele Vue has found that 2 diopters of eyesight astigmatism are detectable down to a 1 mm exit pupil, while 1 diopter is detectable at a 2 mm exit pupil. Dioptrx lenses, therefore, obviate the need for dedicated "astronomical eyeglasses". The primary benefit is the potential for an optimized correction in the amount and orientation of eyesight astigmatism in astronomical viewing. The ability to compensate for both orientation and astigmatism, as your eyesight changes, is another advantage. And, they eliminate eyeglass frame and discomfort problems when viewing with your telescope.