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Objective Diameter | Optics Trade Debates

Welcome to Optics Trade debates. In each episode, we talk about a different topic and try to answer the most common questions we receive about it. Today, we are going to talk about the objective diameter.

The objective diameter is usually found in specification tables of binoculars and riflescopes. It’s important mostly for riflescopes.

Objective diameter is the outer diameter of the housing surrounding the objective lens.

The most common objective diameters in Europe are 30 mm, 48 mm, 56 mm, 58 mm and 62 mm. There are less common dimensions of objective diameters everywhere in between 30 and 80 mm.

This dimension wasn’t important until recent years. It’s important for calculating the correct distance between the barrel and the scope, and consequently the height of the needed rings. The other really important reason is the mounting of covers and adapters for TI an NV clip-on devices.

Objective diameter is sometimes mistaken for the diameter of the objective lens. The objective lens diameter is always stated in the scope’s name.

Some manufacturers don’t specify the objective diameter but we try to list it on all riflescopes that we sell on our web store, so that it’s easier to choose appropriate mounts, covers, and adapters.

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Explanation of the term on our website:

Objective diameter is outside (housing) diameter of the front side (objective) on the rifle scope.

On most rifle scopes objective diameter is bigger than tube diameter. Keep in mind, the last number in the description of rifle scope tells you the size of the objective lens diameter (example: 2 – 7 x 32). Objective diameter is always bigger then lens diameter.

Objective diameter is important to know when buying ring mounts. The bigger the objective diameter the higher mount you will need.

This information is also important for all users of clip-on devices.

objective diameter

Source: Revija Lovec

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