Eyepieces
Terms to know when buying an eyepiece
Exit pupil:
This is the size of the image that comes out of the eyepiece. Ideally it should be close to the size of your dark-adapted pupil – around 5mm to 7mm.
Eye relief:
This tells you how far your eye must be from the eyepiece in order to see the entire field of view. A bigger distance (called longer eye relief) is useful if you wear glasses.
Field of view:
This is sometimes abbreviated to FOV, and is the figure that lets you know how much of the sky you can see through your eyepiece. This measurement is given in degrees.
Power:
This is just another name for magnification. A telescope just captures the light – it is the eyepiece that magnifies the image.
Solar Warning : Never look directly at the Sun with the naked eye or with an optic (unless you have
the proper solar filter). This may result into permanent and irreversible eye damage.
Qualities of a Good Telescope Eyepiece
An eyepiece is essentially a mixture of lenses used as a magnifier, the latter being a positive lens but its focal distance. It is important to note here that telescopes use very low power in the starting point to view an object in a telescope.
And with the requirement, it slightly increases the power of the eyepiece, which helps in rendering a better view of an object. The functions of an eyepiece mainly depend upon the light source, which helps in magnifying the image to be visible to our eyes.
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They mostly use ocular lenses that are available in variety and can be used in telescopes and even microscopes. The name of the lanes became so as they are used closest to the eye, which makes the names are the mirror of the telescope collect light in creating the focus of an image. This type of telescope can be used at home or for professional use.
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High focal point: helps in providing a better view
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Real view of an image: gives actual view of the object
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A clear view of an image: gives a clear view to get accurate data
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Helps in manipulating the eyepiece telescope works as binocular, and even they are fixed to binocular to give a programmed view.
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Eyepieces are interchangeable: to provide comfort
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The eyepieces can be adjusted as per requirement.
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It helps in increasing or decreasing magnifying point of a telescope
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Gives different view from different angles of the same object
What are the different types of eyepieces?
There are many types of eyepieces available in the market:
Plossl eyepiece
Plossls have a wide field of view and can be used successfully for terrestrial as well as deep-sky viewing. It gives relief to the eye for viewing. It has two back-to-back lens systems. Its production is quite cheap.
Radian eyepiece
Radian is a new type of eyepiece in the market which provides a very compatible view. The focal length of these eyepieces is made to provide eye relief and good viewing. It’s very user-friendly for everyone else and even for people wearing eyeglasses.
Nagler eyepiece
Nagler’s most impressive quality is its huge field of view. Naglers go the extra mile to develop an ultra-wide field to give perfection to give a proper and clear view.
Orthoscopic eyepiece
Orthoscopic are good little eyepieces made with a four-element optical system that gives excellent eye relief. The design also keeps down the quantity of sunshine that's refracted within the system very effectively. They come in most useful for making observations of the Moon and planets.
Nagler eyepiece
It isn’t an eyepiece but works with an eyepiece to increase the magnification. One can double or triple the magnification from the eyepiece alone. 
Which Eyepiece to Buy?
It specifically depends on your choice and needs when buying them still there are specific points which one should keep in mind while buying them.
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Eyepieces and telescopes are signified by their focal lengths.                                                   
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All about magnification, and too high a magnification can spoil the view.
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Different celestial objects are best seen at different magnifications
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Typically be marked on the body along with its focal length.
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Apparent field of view divided by the magnification.
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Build quality of your eyepiece and particularly its lens basics. Quite exotic glass is a prerequisite.
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Non-reflective coatings are also vital and reduce the contrast and spoil the view.
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Non-reflective coating quality is an essential factor in the choice of eyepieces.
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Selection of eyepieces to match each of your different observing objectives.
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Ensuring that the inside of the eyepiece body is a very matt black.
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Best eyepieces are ‘fully multi-coated, though ‘multi-coated eyepieces' are still good.
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Manufactured to an exceptionally high standard.
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Multiple glass lenses inside that fit together