This is an ignorant question, but when you zoom in full, is every light dot a star? Or is it noise, like you get with a poorly lighted photo?
Then you take a look at the XDF[1], showing ~5500 galaxies like this one in a tiny angular diameter, and you realize how big the Universe is.
[1] http://hubblesite.org/newscenter/archive/releases/2012/37/im...
So, back of the envelope calculation multiplying 5500 by the area of the full sky (as though the earth were invisible) we get ~242 billion galaxies, which is close to what this[2] claims at 100 to 200 billion galaxies.
Space is big.
1. https://en.wikipedia.org/wiki/Hubble_eXtreme_Deep_Field
2. http://www.space.com/25303-how-many-galaxies-are-in-the-univ...
The Hubble Ultra-Deep Field (of which the Extreme Deep Field is a part) is one thirteen-millionth part of the full sky. [1]
The full sky is about 41,253 square degrees in size. [2]
I think the HXDF is one 32-millionth of the full sky. If so, multiplying 32 million by the 5500 galaxies in the XDF gives on the order of 200 billion galaxies, as you said.
[0] https://en.wikipedia.org/wiki/Angular_diameter
1. https://en.wikipedia.org/wiki/Hubble_eXtreme_Deep_Field 2. https://en.wikipedia.org/wiki/Hubble_eXtreme_Deep_Field#/med...