BRESSER ICD 30.5mm Widefield Eyepiece 15x

The 10x eyepiece is suitable for all microscopes with 23.2mm eyepiece tube diameter. This diameter is widely used in stereo microscopes, also from other brands or manufacturers. Please select the eyepiece magnification in correspondence to the objective you are using. A low objective magnification allows for a higher magnification of the eyepiece. For example, combined with 4x or 10x objectives, eyepieces with 20x or 25x magnification can be used without loss of image quality. With a 100x objective, a 10x or 12.5x eyepiece is usually the highest recommended eyepiece magnification.

To calculate the maximum useful magnification, consider the numerical aperture (N. A.)  of the objective lens:
numerical aperture of the objective lens x 1000 = max. useful magnification
Here is a typical example: for a 10x objective with numerical aperture NA 0.25, a maximum of 250x magnification can be realized. This is realized with a 25x eyepiece. The numerical aperture is usually printed besides the magnification factor on many objectives.

Magnifications beyond the max. useful magnification do not show any further details (so-called “empty magnification”) and are therefore not recommended.