Ultra-Series 2", 21mm, 100° eyepiece

This is the angle of aperture of an eyepiece.

The optical elements are treated with ultra-thin coatings. Among others, there are anti-reflective coatings for reducing, and dielectric coatings for increasing reflection.

Specifies the product's connection or connection thread on the telescope connection end. The same adapter dimension must always be available on the telescope.

A standard measurement for accessories, expressed as 2 inches. 2" is equal to 50.8 millimetres.

Used to connect a filter to the accessory.

Eyepieces are important accessories for every telescope.