main mirror of the Hubble Space Telescope, measuring 2.4 meters (94.5
inches) in diameter. The primary mirror captures light from objects
in space and focuses it toward the secondary mirror.
A smaller mirror (0.3 meters, or 12.2 inches) that redirects the light
coming from the primary mirror through a hole in the center of the primary
mirror and onward to the science instruments.
Where Hubble's images are formed. The mirrors focus the starlight onto
the focal plane, which is roughly the size of a dinner plate. The light
is then picked up by the science instruments.
Corrective apparatus "worn" by each of the early science instruments to compensate
for the imperfect shape of the primary mirror. Later science instruments had corrective measures built-in, eventually making the Corrective Optics Space Telescope Axial Replacement (COSTAR) redunant. COSTAR was removed in 2009 during Servicing Mission 4.