So how far can the human eye see?
Earth's surface curves out of sight at a distance of 3.1 miles
Now if the Earth were flat, which it's NOT, on a dark night, you could even see a candle flame flickering up to 30 miles.
There's no limit to how deep the eye can see into space as long as the object is big and bright enough to be seen.
The record for the most distant object capable of being seen is held by this object: GRB 080319B. It was a Gamma-ray burst and had a peak magnitude of 5.7 and remained visible to human eyes for approximately 30 seconds.
It was 7.5 billion light-years away. Those photos started their journey to us before the Earth was even formed. "The photons started their journey 7.5 billion years ago."
Until this gamma-ray burst event, the Triangulum Galaxy, at a distance of about 2.9 million light-years, was the most distant permanent object visible to the naked eye, although others contend the Andromeda Galaxy is the most distant object that can be seen with the unaided eye.
