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FREN

Tools ·Glossary

Field curvature

In French: Courbure de champ

A telescope’s sharp image is not flat but slightly curved: when the centre is in focus the edges are not, and the other way round. The eye copes, but a flat sensor shows it. A field flattener corrects it.

Related terms

Field flattener

A lens placed in front of the camera that corrects a refractor’s field curvature, so stars stay sharp to the edge of the frame. It must sit at the right distance from the sensor (often 55 mm). At the eyepiece the eye compensates and it is not needed.

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