Product Description

7101 Diopter Tester

Test eyepieces and lenses

The 7101 is primarily used to check the range and establish the “zero” setting of focusing eyepieces for optical products such as binoculars, rangefinder microscopes, theodolites, spectrometers, telescopes, etc. It may be used for measuring the power of a lens (within range), measuring field curvature of a lens, determining the range of focusing eyepiece, and measuring astigmatism of a telescope.

The 7101 has a range of 9 diopters (from +4 to −5). Its scale is calibrated in major numbered divisions of whole diopters, with the smallest divisions equal to 0.2 diopters. Estimates to 0.1 diopter are easily and accurately made.


Diameter: 1 3/8″ (34.9mm)
Length (closed): 3 ½” (89mm)
Length under working conditions: 3½” (89mm)
Field of view: 12°, 40′ (12.2m)
Aperture: 13 mm
Diameter of exit pupil: 4 ¼ mm
Magnification: 3x
Minimum Focus: 8″
Range: 9 diopters, from +4 to -5
Smallest division 0.2 diopters, with whole diopters numbered
Zero setting: At infinity (for perfectly collimated light)
Approx. weight: 1½ lbs. (0.7 kg)


English (PDF)