Telescopes

Topic Content:

Telescopes are instruments used for viewing distant objects such as stars and meteors. They make distant objects appear brighter, clearer and magnified.

Types of telescopes include:

• Astronomical telescope
• Galilean telescope

Astronomical Telescope:

The simplest telescope is the astronomical telescope.

An astronomical telescope consists of two converging lenses, the objective lens has a long focal length and the eyepiece has a short focal length. The objective forms a real diminished image of a distant object at its focal length.

Rays from distant objects such as stars are nearly parallel on reaching the objective lens and form a real, inverted, diminished image of the object at the focus of the objective lens, F_o .

Astronomical Telescope with Final Image at Near Point:

When the image of a telescope forms an image at near point, the telescope is not in normal adjustment, the eye is accommodated,