Televue Ethos 100-deg FOV Eyepiece - 21mm

Model # ETH-21.0
Focal Length (mm) 21
Barrel Size (in.) 2"
Apparent Field of View (deg.) 100
Eye Relief (mm) 15
Weight (lb / oz) 2.25 / 36.0
Field Stop (mm) 36.2

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The 21mm focal length completes the logical set of 21mm/13mm/8mm and nicely juxtaposes the 17mm/10mm/6mm combination. Each step within these two sets approaches a 3x field area gain. The 21mm's effective field stop diameter is 36.2mm, bringing its true field close to the 35mm Panoptic (38.7mm Field Stop diameter). Its true field is also larger than the 26mm Nagler with its 35mm effective field stop diameter.


Data sheet

Barrel Diameter
Wide Angle
Focal Length
21 mm