Two-Lens Telescope
Two lenses in a tube magnify distant objects — build the instrument that reshaped astronomy.
Start building ↓The build
Fit the objective
Mount the larger, weaker lens at the front of a tube.
Fit the eyepiece
Mount the small strong lens in a sliding inner tube.
Slide to focus
Move the inner tube until a distant object snaps sharp.
Observe
Look at far signs or the Moon (never the Sun).
The objective lens forms a small real image of distant light, and the eyepiece acts as a magnifier that enlarges that image for your eye.
A closer look
Magnification roughly equals the objective's focal length divided by the eyepiece's, which is why a long front lens helps.
Variables to test
- 1 Swap eyepieces — how does magnification change?
- 2 Why does the image appear upside down?
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