The most important feature of a telescope is its aperture. Aperture is the diameter of the objective lens or primary mirror. It determines how much light the telescope can collect, which in turn determines how faint objects it can see. The larger the aperture, the more light the telescope can collect, and the fainter objects it can see.

For example, a telescope with an aperture of 100mm can collect 100 times more light than a telescope with an aperture of 10mm. This means that the 100mm telescope can see objects that are 10 times fainter than the 10mm telescope.

The aperture of a telescope is also important for determining its resolving power. Resolving power is the ability to distinguish between two closely spaced objects. The larger the aperture, the greater the resolving power of the telescope.

In general, the larger the aperture of a telescope, the better it will be. However, larger telescopes are also more expensive and more difficult to use. As a result, it is important to choose a telescope with an aperture that is appropriate for your needs and budget.