What optical penalty is associated with light passing through a single lens in less expensive Refractors?

Answer

Chromatic aberration

The fundamental optical penalty inherent in basic lens-based designs, particularly in less expensive refractors built with a single lens element, is known as chromatic aberration. This phenomenon occurs because the various colors, or wavelengths, present in white light do not all bend at the exact same angle when passing through the glass. When these colors fail to converge precisely at the same focal point, it results in a visible colored fringe surrounding bright objects when viewed under high magnification. This fringing is typically observed as purple or blue discoloration around the edges of the target. To mitigate this significant issue for high-contrast viewing or astrophotography, manufacturers must advance to more complex, multi-element designs like triplets.

What optical penalty is associated with light passing through a single lens in less expensive Refractors?

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