The Hubble Telescope's Field of View

Size of the Moon Illusion
The Angular Size of the Moon
HST Field of View
WFPC Moon Mosaic
Copernicus Detail

Thumb with sand grain held below the full moon.
The Hubble Telescopes's Advanced Camera for Surveys (ACS), installed in 2002, has a square field of view, 3.4 mins of arc across - one ninth the width of the Moon. It captures only a small portion of the sky - about as much as would be covered by a grain of sand balanced on the tip of a thumb held at arm's length.

The Hubble Telescopes's Wide Field Planetary Camera (WFPC), in use from 1995 to 2002 had an irregular field, 2.7 mins of arc across.

STScI-PR99-14 April 16, 1999 Hubble Shoots the Moon
STScI - Advanced Camera for Surveys
Michael Gallagher
1999 and 2003
wfpc2 image