HOW FAR CAN A HUMAN EYE SEE? without any special equipments like telescope..?
492923
The eye it not limited by distance;\n\nit responds to photons hitting the retina, it does not care how far the photons have travelled.\neg you can see a bright star further away than a dim one because it emits more photons. A telescope serves to collect more photons.\nIn a dark room you cannot see even close objects.
265230
dust\nDon't use a mirror to look at a laser. don't use anything to look at a laser unless you know what you are doing. not even one of those 'meeting pointers'. it could very easily damage your eye and cause blindness. don't even shine a laser at an object that is not intended to receive laser energy. you could crash a plane or hurt or kill someone else.
506536
It's the only object outside our own galaxy visible with the naked eye. But you have to be in a very dark area, i.e. well away from any major cities.
1105433
You could, but it would be huge overkill. The telescope's objective (lens or mirror) limits the resolution of the image in the focal plane. So you'd be using a microscope to examine (at huge magnification) that resolution-limited image. You'd see nothing but a lot of fuzz, even when in focus; and it would be dim fuzz at that, because you'd only be capturing a tiny fraction of the available light.\n\nI'd stick to standard eyepieces.
28127
You can see about 4 miles to a flat horizon on the Earth. So from one horizon to the other would be 8 miles. (On the Moon, it would only be 3 miles-- the horizon is only a mile and a half away.)
126938
you don't need to look very far
149443
It depends on how tall you are.  The taller you are the farther you can see.  Most people can see between 6 and 7 miles if the air is really clear with no haze, fog, mist, etc.
167535
If your telescope has a finder scope (a much smaller telescope mounted on the main telescope) stick with observing objects that you can locate in it. In order to observe more distant objects that you can't see with either your naked eye or the finder scope, you'll need to learn about the celestial coordinate system (right ascension and declination) There are hundreds of fascinating objects that even smaller telescopes can bring into your vision, but can't be easily located without knowing their celestial coordinates and how to locate those coordinates.
920243
Make a Simple Telescope\nYou will need the following: \ntwo magnifying glasses - perhaps 1 - 1.5 inches (2.5-3 cm) diameter (it works best if one is larger than the other) \na cardboard tube - paper towel roll or gift-wrapping paper roll (it helps if it is long) \nduct tape \nscissors \na ruler, yard stick, or tape measure \nsheet of printed paper - newspaper or magazine will do \nTo assemble your telescope, do the following: \nGet the two magnifying glasses and a sheet of printed paper. \nHold one magnifying glass (the bigger one) between you and the paper. The image of the print will look blurry. \nPlace the second magnifying glass between your eye and the first magnifying glass. \nMove the second glass forward or backward until the print comes into sharp focus. You will notice that the print appears larger and upside down. \nHave a friend measure the distance between the two magnifying glasses and write the distance down. \nCut a slot in the cardboard tube near the front opening about an inch (2.5 cm) away. Do not cut all the way through the tube. The slot should be able to hold the large magnifying glass. \nCut a second slot in the tube the same distance from the first slot as your friend wrote down. This is where the second magnifying glass will go. \nPlace the two magnifying glasses in their slots (big one at front, little one at back) and tape them in with the duct tape \nLeave about 0.5 - 1 inch (1 - 2 cm) of tube behind the small magnifying glass and cut off any excess tube remaining. \nCheck to see that it works by looking at the printed page. You may have to play slightly to get the exact distances between the two glasses right so that the image comes to a focus. \nWith your telescope, you should be able to see the moon and some star clusters as well as birds, etc. \n\n+++++++++++++++++++++++\n\nMake a Simple Microscope\nYou can make a simple microscope by using magnifying glasses and paper: \nGet two magnifying glasses and a sheet of printed paper. \nHold one magnifying glass a short distance above the paper. The image of the print will look a little bit larger. \nPlace the second magnifying glass between your eye and the first magnifying glass. \nMove the second glass up or down until the print comes into sharp focus. You will notice that the print appears larger than it does in the first magnifying glass. \n\nI've included two links below for this and other info.\n\nMyst
523034
The first answer *edit* was modified so now what I say here makes no sense - but her website confirms that I am right (5km = ~3 miles)*. If we want to know the distance to the horizon from a vantage point on a sphere, the only thing that matters is the radius of the sphere and the height of the vantage point.\n\nSo, assume you are standing with your eyes at 5'5" looking out at a calm ocean. You will typically be able to view the sea surface at 3 arcminutes, or roughly 5 kilometers, out to sea. Beyond that you would still be able to see ships and whatever else sticking above the water quite easily, but upon close inspection realise they appear deeper in the water than they actually are.\n\nAlso note that light bends around mass, so you might be able to "see" farther than your actual vantage point, but I'm not doing that calculation.\n\nI assume that people who have values higher than mine are thinking about higher vantage points than mine, because I think my estimations are close and I'm positive that my logic is right. Correct me if my numbers are off, but I'd like to know why.
417578
"Astronomers can use parallax to find distances to objects much farther even than planets. To calculate the distance to a star, astronomers observe it from different places along Earth's orbit around the Sun. If they measure the object's position several months apart, their "two eyes" will have a separation of well over 100 million miles! \n\nNow astronomers have technologies to measure distances to other planets more directly. When we have a spacecraft at another planet, we know the time it takes a radio signal to travel between Earth and the spacecraft. We can also send a powerful radar signal toward a planet and time how long it takes for the echo to return. Astronomers know how fast these signals travel (the speed of light), so measuring how long they take makes it easy to calculate the distance very accurately."
596764
Magnification is dimensionless\n\nWhat is the focal length of the concave mirror in b\n\nConvex mirror has wider field of view.
269241
It depends on your eye level above ground.   Typically, it's in the range of 2-3 miles, depending on your height.  You can find out exactly at the link below.
1056956
No, I read an article and it said that you need a strong telescope and lots and lots of astronomy experience. I was hoping I'd be able to see it too, but I have neither!
1068112
We just don't know yet cause that Hubble Telescope is only strong enough to see a certain distance. \n\nScientifically we just don't know and I am not at liberty to guess....Neither are you. hehe
932806
If it is for the same person then the results mean \n\nLeft Eye - You can see at 20 feet what an average person sees at 50 feet \nRight Eye - You can see at 20 feet what an average person sees at 300 feet \n\nYou need glasses.
879967
if you have a good enough telescope - you can see some stuff.\nyou can also see the robotic tractor that was left on Mars. (though you need more than a standard telescope for that)\nIt has been done by many people