| Why do we have trouble clearly seeing objects | | | | and move it back until the sheet covers our |
| that are too far away without the use of one of | | | | entire field of vision, we would say that each card |
| the many telescopes for sale? There are many | | | | takes up only 1/25th of our field of vision. This |
| reasons, but two of the main ones are 1) the | | | | means that, on average, each card only has 4% |
| objects take up too little room in our field of view | | | | of our photoreceptors trained upon it. Therefore |
| and 2) they are not bright enough. Let us explore | | | | we are receiving, on average, only 4% of the |
| the first of these two factors in depth and | | | | information from each card as we received when |
| discuss how all of the telescopes for sale work to | | | | the card was close. |
| improve the situation. | | | | Thus, the farther away an object is - the smaller |
| We can think of the retina as the movie screen in | | | | amount of our field of view it takes up. As an |
| our eye. Light entering the pupil of the eye is | | | | object becomes smaller in our field of view, it |
| focused onto the retina which covers the back | | | | impacts fewer and fewer photoreceptors. The |
| surface of the eye. The retina is covered with | | | | fewer photoreceptors affected, the less total |
| millions of photoreceptor cells - commonly known | | | | optical information collected and the less clear the |
| as rods and cones. Photoreceptor cells are cells | | | | image becomes. At some point, the incoming light |
| that convert light into nerve impulses that are | | | | will affect such a low number of photoreceptors |
| then transmitted to the brain where they can be | | | | that the object will become invisible to us. |
| formed into the image that we "see". | | | | In the many telescopes for sale, this is where the |
| When an object is close to us, it takes up a large | | | | eyepiece comes into play. The large objective lens |
| percentage of our field of view. As an extreme | | | | (in refracting telescopes) or primary mirror (in |
| example, if we hold a business card up right in | | | | reflecting telescopes) collects incoming light. This |
| front of our eye, all we can see is the business | | | | light is then focused through the eyepiece lens in |
| card. If we hold it so that we can see the entire | | | | order to magnify it. This magnification process |
| card and nothing else, we can say that it takes up | | | | causes the image to get larger, and therefore, |
| 100% of our field of view or it is covering 100% | | | | cover a larger percentage of your field of view. |
| of our retina. This also means that every one of | | | | This, of course causes the image to impact more |
| the millions of photoreceptors is transmitting light | | | | photoreceptors in your eye - and thus - the |
| impulses to the brain from this object. | | | | image becomes clearer. |
| If we now create a 5X5 sheet of business cards | | | | |