Diopter Telescope

The Diopter Telescope or Dioptometer is a focusing telescope measuring the power of lenses in diopters. The results of the measurement can be read off on a graduated scale. The measurements with Diopter Telescopes include following steps:

•  the eyepiece of the Diopter Telescope is rotated until its reticle is seen sharp and clear. The focusing ring is set to zero.

•  the Diopter Telescope is placed with its supporting flange on the eyepiece or the telescope under test. The eyepiece of the telescope under test is rotated until its reticle is seen sharp and clear. This is the zero  setting of the eyepiece.

•  Further measurements are made by rotating the eye-piece under test to the next graduation and focusing the Dioptometer correspondingly. The reading is done directly on the diopter graduated scale.

Key Features

  • The supporting flange of TRIOPTICS Dioptometers is hexagonal (48 mm wide) and removable. After removing the flange,  the  connection thread M 38x1 mm can be used to attach the Dioptometer to custom holders or other devices.

  • The size of the smallest division is important for accurate reading. All TRIOPTICS Dioptometers (except for 3-100-298) have large graduations and permit easy reading and accurate estimation at half of the smallest division. The eyepieces are interchangeable and can be adapted  to  custom  needs.


The Diopter Telescopes have wide applications in the field of optical testing. Most important applications include:

•  Testing diopter graduation, focusing range and infinity („zero“) setting of eyepieces

•  Measurement of power of lenses

•  Testing the astigmatism of telescopes

•  Measuring the field curvature of lenses