## Ken's Eyepiece Corner - Formulas |

Enter two of the three values for the objective diameter, *f*/number, and focal length, then press Compute to calculate the remaining value.

Enter two of the three values for the effective focal length, objective focal length, and Barlow X factor, then press Compute to calculate the remaining value.

Enter two of the three values for the eyepiece field stop, objective focal length, and field angle, then press Compute to calculate the remaining value.

## Field angle (degrees) = (Eyepiece field stop / Objective focal length) * 57.3 degrees/radian |
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Eyepiece field stop |
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Objective focal length |
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Field angle (degrees) |

*(c) Copyright Kenneth L. Hess, 1997, All Rights Reserved*

Please send comments to: ken@KLHess.com