Define Telescopes power with The Help Of Telescope Eyepieces
March 20, 2008
Whenever we look into a camera or a binocular we look into the eye piece, so also when we look into the telescope we place our eye where the eyepiece is placed this helps us to determine the magnification of a lens. The eyepiece can alter the focal length of the telescope and it can help determine the apparent field of view, the width of the object that you wish to see when you look through the telescope.
Usually the focal length of a telescope divided by the telescope eyepieces will give you the power of the lens. Say for example, the focal length of 500 used with a 10mm eyepiece would give you the result in a telescope by making the object appear closer to you by 50 times. A 25mm focal length on an eyepiece will drop the power to 20X2.5mm, one of the smallest commercially available eyepiece sizes that would render a 200Xtelescope.
Does Size Matter?
Sometimes people tend to think that the bigger the telescope power the better will they be able to view the field but that is not always true because the field of view is also affected by the eyepiece, as well as the eye relief measurement to how well you can see through the telescope. The field view here indicates how much of the sky is visible when you look through the telescope eyepiece. If you are using a strong or powerful lens you may be able to see the stars closer to you but then you will be able to see very little of the sky, for example a telescope with a 100-power lens and a field of view of about 50 degrees will fit a typical full moon in the lens.
Features:
There are many features in a telescope and one another feature of the telescope eyepiece is the diameter and though this measurement does not have any direct affect on the magnification power of the telescope it will definitely affect the view of the surrounding of the object that is to be viewed. If the lens has a long focal length and a small barrel size, the view will be restricted to the point of finding the images will be difficult in the sky. To further make you understand the concept connected to the power of the telescope eyepiece if you try looking through a straw with the opposite end of the straw closed or blocked by the wall and then if you try to find a specific spot on the wall while standing about 10 feet away you will not be able to do so.
If you move a foot away from the wall and look at the same spot you will be able to view the spot but then the view will be small because you are standing very close to the wall. Well, the same theory stands true for the telescope eyepiece. And yet another important measurement is referred to as the eye relief. In a term that can be easily understood by the amateur astronomer or for that matter any layman is the distance from the eyepiece glass and your eye, if it is too close your eyelashes may touch the glass and if too far your vision may not be able to focus on the object properly on the telescopes lens.
Summary:
The telescope eyepiece plays an important role in viewing the object and it is not necessary that by using a very powerful telescope lens you will be able to view the object properly, because if you are able to view the object clearly you may not be able to view the sky along with the object because the object will have occupied almost the whole of your telescopes eyepiece. So the eyepiece should always be such that you are not only able to view the object but also the surrounding area too can be viewed if not completely but at least partly.
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