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Thursday, February 25, 2010Using telescope and spotting scope eyepieces  It’s no secret that using two eyes to look through optical instruments like binoculars is easier than using one eye, as when using spotting scopes or a telescopes. A good way to appreciate the advantage of using two eyes for observing is to use a monocular microscope for an hour compared to using a binocular microscope for an hour. Using two eyes does improve visual acuity and it does make for much less eye fatigue for long observing sessions. With spotting scopes and telescopes, there is no binocular eyepiece option, though, so we are stuck with using one eye. So how do we reduce the eye fatigue that occurs when we use only one eye for viewing in a spotting scope or telescope? The first and probably the hardest thing to learn is to keep both eyes open when looking through a spotting scope or a telescope. Leaving one eye open and squinting the other eye shut, as so many people naturally tend to do, creates uneven muscle strain on the muscles that control both eyes – one eye is working and one eye is not, so to speak. This can lead to a very nasty headache at the end of a long session with your spotting scope or telescope, not to mention some blurry vision. Keeping both eyes open reduces the problem, considerably, though it does require some practice. A great aid to keeping both eyes open when using a spotting scopes or telescopes is to use a spotting scope or telescope eyepieces that offer a large glass element against your eye and also a wide field of view. Your off eye, then, is much less likely to distract you – that big wide field of view of these wide-angle eyepieces just draw your working eye in and you soon forget your other eye. Problem is that most zoom eyepieces used on spotting scopes have a rather narrow lens element; only very expensive zoom eyepieces have large lenses. The best option, though, is to use fixed power, wide-angle eyepieces. These eyepieces tend to have the largest possible glass lenses and offer the ultimate in viewing comfort when keeping both eyes open. You want a big, easy to view, picture window view, even when using only one eye? Try the Televue Nagler 22 mm telescope eyepiece, pictured above. Doesn't get better than that. Comments: |
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