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Nagler
82° Apparent Field Eyepieces
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| 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 Diam. (mm) | 27.4 |
| Compare to similar focal lengths | |
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.
To achieve various features requires different design tradeoffs and thus the different types of Nagler eyepieces. The largest possible true fields of view for an 82°' apparent field of view in both 2" and 1¼" formats are achieved with the Nagler Type 5 series, with focal lengths of 31 and 16 mm
Compact size in medium to short focal lengths is achieved with the Nagler Type 6, available in focal lengths of 13, 9, 7, 5, and 3.5 mm.
To achieve eyeglass friendly eye relief without excessively large and heavy designs requires the other two Nagler types. The 22mm Type 4 and 19, 14, 9, 5.5 mm Type 7 with their long eye relief feature adjustable height eyeguards and are best for eyeglass wearers or Dioptrx™ users.