How many exposures were used to make the Hubble Legacy Field? The answer is 7,500 exposures.
The Hubble Legacy Field is a deep composite image assembled from observations collected over 16 years. It combines data from several major Hubble surveys, including the Hubble Ultra-Deep Field, the Hubble eXtreme Deep Field, and the Great Observatories Origins Deep Survey. Together, those observations reveal an estimated 265,000 galaxies.
The 7,500 exposures represent repeated observations through different filters and instruments, not 7,500 separate sky fields. Their combined exposure time totals about 250 days. The field lies in the constellation Fornax, in a region chosen for its low concentration of bright foreground stars and relatively low zodiacal-light interference.
The result lets astronomers study galaxies seen as they existed roughly 13 billion years ago, only about 400 to 800 million years after the Big Bang. The figure 13,308 belongs to a later GOODS data release, making it a plausible but incorrect alternative for this question.