Sky science
Magnification
Direct answer
Magnification is the ratio by which an optical system enlarges a target’s apparent angular size.
It makes an angular image appear larger.
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At a glance
- Found in
- Astronomy & Skywatching
- Related
- Telescope Focal Length, Focal Ratio, Exit Pupil, True Field of View
It makes an angular image appear larger.
A scientific orientation to scale, light, or motion; the article supplies the precise definition.
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The story behind Magnification
Interchangeable eyepieces made variable telescope magnification practical.
A one-minute story
The Wandering Stars
How the moving planets were watched, named and found, and what a transit is.
Why Magnification matters
Magnification can reveal available detail when matched to aperture, seeing, and observer vision.
How to read Magnification
Calculate telescope focal length divided by eyepiece focal length.
Magnification in practice: an example
A 1200-millimeter telescope and 20-millimeter eyepiece produce 60 power.
Where readings of Magnification go wrong
Excess magnification enlarges blur and dims the exit pupil without creating detail.
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
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Common questions
What is magnification?
Magnification is the ratio by which an optical system enlarges a target’s apparent angular size.
What do people get wrong about magnification?
Excess magnification enlarges blur and dims the exit pupil without creating detail.
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