Ok, since it is Friday.
You can see the Andromeda galaxy with the naked eye and that is 2 million light years away.
A galaxy must put out a lot of light but, by the time it reaches us it is spread over a sphere with surface area 50,000 trillion square light years. So each second your eye will capture:
number_of_photons_output_by_galaxy_every_second
* area_of_your_iris
/ 50,000 triilllion square light years
Mercury, Venus, Mars, Jupiter and Saturn are the five brightest naked-eye planets. These planets undergo a regular appearance cycle and several of them can be seen with the naked eye for much of the year, apart from short periods of time when they are too close to the Sun to observe.
Yes well I didn't want to be too pedantic but quite often venus is further away than the sun when it's visible in day light, there I did it!. Oh and during an eclispe you can see the stars too, oh bu66er!
Astronomically interesting, chaps, but before we all get too carried away into space, Icebread only wanted to know ''how far can the eye see when looking out at the sea''!