This depends on a number of factors.
- How Dark Is it
- How good are your eyes
- How Bright Is it
- How big and how bright are the objects you can see
For the convenience I assume that you look from the backyard, on a little dark nights you can observe objects with a brightness of up to Magnitude 4. (The smaller the number the more feller the object.For example, Venus has about magnitude-4
I just quickly checked on a star map.The Andromeda system is 3 million light years. With a magnitude of 3.4 you should be able to see those with your naked eye. It has not succeeded me without a binoculars.
For example, if you take a star, you will encounter the constellation Canis Major, Aludra at 3200 light year.There is a chance that a visible star is still further away. But for now I keep it at this.
It used to be thought that the eye radiated something that is reflected back.That’s how it feels when you look around you. You’ll see objects at a certain distance. In Reality, we only see something when the light reaches the eye. Ultimately, it is ‘ seeing ‘ a brain activity.
The eye consists of several light-sensitive nerve cells.A nerve cell only responds when there is enough light on it. About as much as an antenna dish scanning the universe also has a lower limit of sensitivity. Because of this, the eye cannot see the Big bang, although this radiation reaches US day and night, but we are not sensitive enough to feel or see that radiation.
The Furthest removed object that we can see with the naked eye is the Andromeda Nebula.That’s not a star, but a collection of many stars gathered together.Anyway, the light of the Andromeda Nebula comes fromstars.Those furthest visible stars stand on 2 million light years away from us.(copyNpaste). If you realise that the universe would be about 6 billion years old and we only see 2 million years far, then we can only see a tiny part of the space. Translated to Earth, we can see a circle with a radius of 7 km far.
It is also funny that colors are created by the different color-sensitive nerve cells.One responds to red light, the other on Blue light and the third on green light. The funny thing is that this light is not red, blue or green, but that we see it that way. Probably these colors arise because we see them all three together as white light, but this light is just as minus white. We See it as white.
When you see this, you also understand that a representation of a radio image, such as the recent black hole with a ring of fire, is not a distortion, but a representation of the image translated into the sensitivity of the human eye.
Will depend on who is watching.Someone (human) who is completely color blind and has only rods in his eyes may look further. Some beasts will probably be able to see beyond most people but they can’t say it.