To achieve greatest magnification, the telescope needs:

• A. As small a distance as possible between the object and its image
• B. As large a distance as possible between the object being viewed and its image
• C. A very bright light source
• D. A wide aperture only

Answer: (B)

Magnification in a telescope comes from how the objective forms a real image and how the eyepiece enlarges that image for the eye. When the object is very far away, the light rays entering the objective are nearly parallel, and the objective makes its image at a certain distance behind it. The eyepiece then magnifies that image to produce a larger, easier-to-see angle for the eye. If the distance between the object and that image is larger, the eyepiece can bend the rays into a much larger angle, giving greater apparent size of the object. Therefore, using objects that are very distant (which increases the object–image distance) leads to the greatest magnification. Brightness and aperture affect brightness and light-gathering ability, not how large the image appears. The key to higher magnification is the optics—specifically the combination of focal lengths that governs how much the eyepiece magnifies the formed image.