Nagler
82° Apparent Field Eyepieces
TeleVue.com: Eyepieces > Nagler > 20mm
20-mm
Model #EN5-20.0
Focal Length (mm)20
Barrel Size (in.)2"
Apparent Field of View (deg.)82
Eye Relief (mm)12
Weight (lb / oz)1.04 / 16.6
Field Stop (mm)27.4
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The 20mm Type 5 is a compact 1-pound, 2" eyepiece that fills out the eyepiece line and is a worthy successor to the heaviest commercial eyepiece ever produced: the Nagler 20mm Type 2, which weighed-in at 2.3-lb. when introduced in 1986.

Why Are There 3 Types of Naglers?

To achieve the full magnification range over 82° apparent field of view requires two types: Nagler Type-5 with focal lengths of 31, 26, 20, 16mm and Nagler Type-6 with focal lengths of 13, 11, 9, 7, 5, 3.5, 2.5mm.

The Type-5 permits the largest true field possible (31mm has 42mm field stop), while the shorter focal length Type-6 models are parfocal, with similiar size and weight and all with a comfortable 12mm eye relief.

The Type-4 models feature about 18mm of eye relief and with the "instajust" eyeguard are best for eyeglass wearers or Dioptrx users in their 22, 17, 12mm focal length range.


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