Tele Vue Nagler are now legendary glasses, the construction of which turned out to be groundbreaking and on the basis of which later generations of ultra-wide-angle glasses were created.
“As you probably know, it is customary to name new eyewear designs after their inventors: Kellner, Erfle or Plossl are just a few examples. At the end of the 70's I designed an eyepiece which was innovative enough that I dared to name it with my own name. At the same time, I must admit that even today, when we talk about the >> Nagler << glasses, I feel a certain discomfort.
When I was designing the Naglery, my goal was to achieve the largest possible field of view while maintaining the best possible image quality and comfortable observation. It was about creating the effect of floating in outer space, as if you were not looking through a telescope. " - Al Nagler
Since their invention, Nagler has repeatedly perfected his design, resulting in the now available Type 4, 5 and 6 Naglers.
To obtain the full range of magnification for the 82-degree field of view, three types of Naglers have been designed. Type 6 includes the following focal lengths: 2.5mm, 3.5mm, 5mm, 7mm, 9mm, 11mm and 13mm. All the focal lengths mentioned are parfocal, have a similar distance from the exit pupil to the eyepiece and are of small size. These are 7-element constructions, made of lenses with different refractive index, covered with perfect anti-reflective coatings. Despite short focal lengths, they are characterized by a comfortable exit pupil distance of ± 12 mm. The focal lengths of the 6-type Naglers change by a factor of 1.4 - thanks to such selection of focal lengths, the use of a 2x Barlow lens does not cause duplication of magnification.
Type 5 and a focal length of 31 mm allow you to obtain the largest real field of view. The 31 mm Nagler is a legendary eyepiece, an object of sighs and dreams of the multitude of owners of large Dobsonians. On the other hand, the Type 4 is characterized by the largest distance between the exit pupil and the eyepiece, with the following focal lengths: 12 mm, 17 mm and 22 mm. Eyepieces with 31 mm, 22 mm and 17 mm focal lengths are 2 "eyepieces, the other focal lengths have 1.25" sleeves.