Over 10 straight days during Christmas 1995, the Hubble Space Telescope focused on a small region of the sky in Ursa Major and collected 324 images over more than 100 hours that were combined to reveal a jaw-dropping treasure trove of more than 3,000 galaxies, an iconic image known as the Hubble Deep Field North. Subsequent observing sessions peered even deeper into the cosmos, capturing ever more comprehensive views of infant galaxies forming in the wake of the Big Bang.
The eXtreme Deep Field, of XDF, combined 10 years of Hubble photos covering a patch of sky near the center of the Hubble Ultra Deep Field, a small region of space in the constellation Fornax that was imaged by Hubble in 2003 and 2004. The XDF, originally released in 2012, is even more sensitive, featuring about 5,500 galaxies within its smaller field of view. The faintest galaxies detected are one-ten-billionth as bright as what the human eye can see.
Here is a labeled view that identifies several key supernovas and some of the most distant (high z) galaxies observed to that point.
This view shows the XDF field of view compared to the moon: