Due to differences in vision of the eyes (such as normal eyes, nearsighted eyes, hyperopia, etc.), as an eyepiece of a magnifying glass, the engraved lines on the reticle must be seen at various positions (the line is the thinnest at this time). Dioptric adjustment refers to adjusting the distance of the eyepiece relative to the reticle, so that the operator can see the reticle on the reticle to the clearest. Failure to adjust the visibility will affect the accuracy of the measurement.

The correct way to adjust the gaze is to adjust the eyepiece from far to near with respect to the reticle until you see the reticle on the reticle. This method can reduce eye fatigue.

Some telescopes have a range reticle. Many people are not sure about the method of use. There are vertical division and horizontal division on the telescope reticle. The division is 5 mils and the score is 10 secret places.