Sky science
Eyepiece
Direct answer
Eyepiece: An Eyepiece is the lens assembly that magnifies and presents a telescope’s focal-plane image to the eye.
It is the observer-facing optical end of a visual telescope.
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At a glance
- Found in
- Astronomy & Skywatching
- Related
- True Field of View, Apparent Field of View, Objective Lens, Primary Mirror
It is the observer-facing optical end of a visual telescope.
A scientific orientation to scale, light, or motion; the article supplies the precise definition.
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The story behind Eyepiece
From simple two-element forms, eyepieces evolved into corrected wide-field designs.
A one-minute story
The Wandering Stars
How the moving planets were watched, named and found, and what a transit is.
Why Eyepiece matters
Eyepiece sets magnification, apparent field, eye relief, and exit pupil with the telescope.
How to read Eyepiece
Choose focal length and design for target, seeing, and observer comfort.
Eyepiece in practice: an example
Changing from a 25-millimeter to 10-millimeter eyepiece increases magnification.
Where readings of Eyepiece go wrong
An eyepiece solar filter near the focus is unsafe; filter the front aperture instead.
Sources and editorial method
Research references used for this entry include:
- European Southern Observatory: Technology for Telescopes - Observatory reference for aperture, angular resolution, atmospheric seeing, mirrors, and telescope technology.
- NASA Science: Eclipse Viewing Safety - Official solar-viewing guidance for eyes, cameras, binoculars, and telescopes.
- Source
- The Great Almanac Dictionary
- Category
- Astronomy & Skywatching
- Last updated
- 2026-09-26
Choose an eyepiece intentionally
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Common questions
What is an Eyepiece?
An Eyepiece is the lens assembly that magnifies and presents a telescope’s focal-plane image to the eye.
What do people get wrong about an Eyepiece?
An eyepiece solar filter near the focus is unsafe; filter the front aperture instead.
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