Sky science
True Field of View
Direct answer
True Field of View is the actual angular width of sky visible through an optical setup.
It is how much sky the instrument shows.
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At a glance
- Found in
- Astronomy & Skywatching
- Related
- Magnification, Exit Pupil, Apparent Field of View, Eyepiece
It is how much sky the instrument shows.
A scientific orientation to scale, light, or motion; the article supplies the precise definition.
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The story behind True Field of View
Wide-field eyepieces and photographic systems expanded practical sky coverage.
A one-minute story
The Wandering Stars
How the moving planets were watched, named and found, and what a transit is.
Why True Field of View matters
True Field of View determines whether a target, star hop, or extended object fits in one view.
How to read True Field of View
Measure by drift timing or calculate from the field stop for accuracy.
True Field of View in practice: an example
A two-degree true field spans roughly four apparent full-Moon diameters.
Where readings of True Field of View go wrong
The apparent-field divided by magnification formula is only approximate.
Sources and editorial method
Research references used for this entry include:
- NASA Science: Skywatching FAQ - NASA guidance for observing stars, planets, constellations, and changing sky events.
- European Southern Observatory: Technology for Telescopes - Observatory reference for aperture, angular resolution, atmospheric seeing, mirrors, and telescope technology.
- Source
- The Great Almanac Dictionary
- Category
- Astronomy & Skywatching
- Last updated
- 2026-09-26
Frame the right amount of sky
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Common questions
What is True Field of View?
True Field of View is the actual angular width of sky visible through an optical setup.
What do people get wrong about True Field of View?
The apparent-field divided by magnification formula is only approximate.
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