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Telescope Field of View — result sheet
Estimate telescope magnification, true angular field of view, and exit pupil from telescope and eyepiece specifications.
Inputs used
Results
Visual chart
Breakdown
Calculation steps
Returned data table
Formula and methodology
Formula: Magnification M = Fₜ/Fₑ; true FOV ≈ apparent FOV/M; exit pupil = aperture/M.
A telescope and eyepiece form an optical system whose magnification is the telescope focal length divided by the eyepiece focal length. A first-order true field-of-view estimate divides the eyepiece's apparent field by that magnification, while exit pupil relates the telescope aperture to the same magnification.
This result follows the calculator's declared inputs, precision, validation boundaries, and model limits.
Input contract
- Telescope focal length — mm; minimum 1.0E-6; maximum 1000000000
- Eyepiece focal length — mm; minimum 1.0E-6; maximum 1000000000
- Eyepiece apparent field of view — °; minimum 1.0E-6; maximum 360
- Telescope aperture — mm; minimum 1.0E-6; maximum 1000000000
Worked example
| Input | Value |
|---|---|
| Telescope focal length | 1200 |
| Eyepiece focal length | 7.5 |
| Eyepiece apparent field of view | 52 |
| Telescope aperture | 200 |
Magnification = 160×, true field ≈ 0.325°, and exit pupil = 1.25 mm.
Assumptions and limits
- The eyepiece apparent field is the manufacturer's angular specification and the simple apparent-FOV-over-magnification estimate is appropriate.
- Focal lengths and aperture use the same length unit; optical stop geometry, distortion, vignetting, and camera-sensor field are not modeled.
- The result is an optical planning estimate, not a guarantee of what a particular telescope will show under atmospheric or mechanical conditions.
Calculator note
Source and methodology
Use the official WorldCalculate methodology policy for the source, formula, precision, and boundary standards behind this calculator.
Planning estimate, not financial, medical, legal, or professional advice. © WorldCalculate — reuse with attribution. Built and curated by Hassan ALRowaie.
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