Field Eyepiece

Lenses and mirrors are the elements used to collect and view focused light in telescopes. Mirrors are the medium for focusing in reflector telescopes, while lenses are the medium in refractors. Each type has its own distinct advantages and disadvantages. Refractor type telescopes use lenses. These lenses bend the light when it enters the telescope from the distant object being viewed through it. Because of this refraction it is possible to closely view a distant object. The telescope has two lenses, with one slightly larger.

The eyepiece in the telescope is generally a small lens. Some telescope however, may not use lenses for the eyepiece at all. The eyepiece, in any case, is the most important element of a telescope. It is the element which lets you see correctly whatever it is that you want to focus on. These eyepieces are adjustable and are of a low power. Adjusting the eyepiece allows you to change the magnification factor. What kind of lens you use for the eyepiece is a personal choice. In today's age, several different kinds of eyepieces are available in the market. Because of this motley available, choosing the correct eyepiece fro your requirement may be a difficult task. As a result, you should concentrate on defining the criteria you think are important for your choice. The depth of field, optical quality, sharpness, clarity, brightness, market price, barrel size and how it affects your eyesight are some of the major points of concern. However these criteria always remain individual prerogatives.

Lens designs used in older telescopes go by the name of Huygens and Ramsden. Professional astronomers are advised to not use these lenses anymore as they are not of superior quality, even though they are comparatively less expensive than other market lenses. These lenses also do not provide correction for chromatic aberration or the light circles that form around brighter objects when they are viewed.

Professional astronomers use orthoscopic lenses that are designed specifically for professional stargazing. Even amateurs will find these lenses good for their telescopes. The orthoscopic telescopes use four lenses in the eyepiece, and have a 45 degree field of vision (FOV). Since the eyepiece is the element most important to the quality of a telescope, this design is a winner. The lenses do not strain the user's eyes, and can be used even for viewing closer objects like planets.

For a person with a moderate budget, a Barlow lens is a viable option. The design provides average quality but is a good bargain. It does not burn a hole in one's pocket, and yet is not of inferior quality because of its cost. The range at which this lens is available starts at a low $30 and goes up to $70. The magnification factor is generally not enough for professional use, however for amateurs it should be enough. For hobbyists, it is an ideal lens.

When you're looking for lenses for a telescope, it is important that you determine criteria that most comprehensively fulfill your needs from the lens. Adjustable lenses is a good option as it means you can view objects which are not too far, as well as distant stars with it, and thus obtain the best deal your money can buy you.

Download free hubble image space telescope as well as learning more about refractor vs reflector telescopes when you visit http://www.howdotelescopeswork.com, the online portal for free resource on telescopes making and usage

Telrads and telescopes..?

Which has larger field of view, a 1200mm telescope with a 25mm eyepiece (48x magnification) or the Telrad?

I'm not sure what the FoV of the Telrad is...?

Katekebo is correct again.

I'd just add that in my scope at 48x, i get just over half a degree, maybe 40 minutes of arc. This isn't an expensive eyepiece. It's the included 25 mm plossl.

My 9x50 finder gives me 5 degrees or so. And that's the point of a finder - giving you a wider field of view so you can find stuff.

Many people like a red dot finder or a Telrad. I'm sure it's because you have such huge field of view. And it can be frustrating to located something with my 9x50 finder - especially since you have to twist your head so far while bending over and holding your head steady, while man handling the dob, and what were you looking for anyway? But a little magnification and alot of light gathering lets me look for smaller, dimmer stuff. And besides, my computer got me close to the object. I hardly need a finder at all. My way of coping with dew on my 9x50 is to leave the lens caps on. Who needs a heater? If the thing ever dews up, i'll just pop it off and put it inside my coat for a few minutes.




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