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Apparent field of view is the angle change from one side of the field in the eyepiece to the other. Your eye subtends this angle when moving from edge to edge.
True Field is the actual field of view on the sky that the eyepiece sees.
Keep the magnification the same, and you can see that as the apparent field gets larger, so does the True Field on the sky.
A 100 degree apparent field eyepiece will see a True Field twice as wide as a 50 degree apparent field eyepiece of the same focal length.
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