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Telescope Primary Mirror Sizes Compared

Diagram of the mirror sizes of the Spitzer, Hubble, and James Webb space telescopes relative to each other. Spitzer has a 0.85-meter diameter mirror, Hubble has a 2.4-meter diameter mirror, and Webb has a 6.6-meter diameter mirror. Spitzer’s and Hubble’s mirror are a single disk with a hole in their centers to allow light through to its science instruments. Webb’s mirror is composed of 18 hexagonal segments and also has a hole in its center to allow light through to its science instruments.

In terms of light-gathering capability, the most important component of a telescope is its primary mirror. The larger the mirror, the more light it can collect, and the smaller, dimmer, and more distant objects it can detect. Webb’s mirror has an area more than 5 times greater than Hubble’s and 45 times greater than Spitzer’s.

  • Release Date
    May 31, 2018
  • Credit
    Image: NASA, ESA, CSA, STScI

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Last Updated
Aug 28, 2025
Contact
Media

Laura Betz
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
laura.e.betz@nasa.gov

Image Credit

NASA, ESA, CSA, STScI

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