| When beginning astronomers start looking at | | | | degrees, which indicates how far a person needs |
| telescopes, one of the least understood aspects | | | | to move their eye in order to look from one end |
| of these optical instruments are simple telescope | | | | of the image to the other. Essentially, it is a |
| eyepieces. While lenses and mirrors and designs | | | | measure of the peripheral vision available to the |
| are easy to grasp, the actual eyepiece itself can | | | | person looking through the eyepiece. Depending |
| be somewhat confusing. However, they are vital | | | | on the design of the telescope eyepiece, the |
| parts of the telescope, as they provide the final | | | | apparent field of view can range from 40 to 82 |
| creation and magnification of the telescope image | | | | degrees. Obviously, the narrower fields of view |
| and they are the one part of the telescope that | | | | give the feeling of looking down a tunnel, making |
| spends its time in almost constant contact with | | | | it more difficult to scan the sky and find objects. |
| the person using it. All of which means that | | | | However, the field of view and image clarity are |
| telescope eyepieces are important considerations | | | | not the only concerns with telescope eyepieces. A |
| when putting together a telescope. | | | | major, but often overlooked, trait is that of eye |
| When looking at telescope eyepieces, remember | | | | relief. This is the distance between the eye and |
| that you are essentially paying for the lenses in | | | | the actual lens surface and it is vital that people |
| the eyepiece. The more an eyepiece costs, the | | | | understand its importance. After all, this can |
| better the lenses inside and the better the image | | | | affect the person using the telescope by simply |
| it creates. And, because the rest of the telescope | | | | making it uncomfortable or difficult to use the |
| is only as good as the image that reaches the | | | | telescope. If someone doesn't have room to |
| user's eye, it is well worth the while to invest a | | | | wear their glasses when they look through the |
| little extra in the eyepieces to be used on a good | | | | eyepiece, or their eyelashes rub against the lens, |
| telescope. | | | | it is simply not worth the effort to use the |
| It is also good to remember that image quality of | | | | telescope. And if someone's eyelashes are rubbing |
| telescope eyepieces can be affected by the | | | | against the lens, it is transferring dust and oils to |
| design of the eyepiece. For instance, Huygens | | | | the lens, degrading the image and, in fact, making |
| eyepieces can create chromatic aberrations, Erfle | | | | the telescope less effective. Of course, the only |
| eyepieces can produce some ghost images, and | | | | way to really find the right eye relief is to try out |
| Plossl eyepieces tend to have some astigmatism | | | | several telescope eyepieces and see which ones |
| around the edges of the image. So, when | | | | feel right. |
| choosing eyepieces, it is also a good idea to | | | | Overall, telescope eyepieces are best judged |
| understand the limits of each design and what | | | | through experience, which means that trying out |
| sort of work each design is suited to. | | | | several designs and models is the best way to |
| Another aspect to consider when choosing | | | | figure out what works best. But, with a little trial |
| telescope eyepieces is the apparent field of view. | | | | and error, the right telescope eyepieces can |
| This is the apparent width of the image, in | | | | make their way into your telescope kit. |