Posts Tagged ‘Lens Elements’
Telescope Eyepieces
An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. It is so named because it is usually the lens that is closest to the eye when someone looks through the device. The objective lens or mirror collects light and brings it to focus creating an image. The eyepiece is placed at the focal point of the objective to magnify this image. The amount of magnification depends on the focal length of the eyepiece.
An eyepiece consists of several "lens elements" in a housing, with a "barrel" on one end. The barrel is shaped to fit in a special opening of the instrument to which it is attached. The image can be focused by moving the eyepiece nearer and further from the objective. Most instruments have a focusing mechanism to allow movement of the shaft in which the eyepiece is mounted, without needing to manipulate the eyepiece directly.
The eyepieces of binoculars are usually permanently mounted in the binoculars, causing them to have a pre-determined magnification and field of view. With telescopes and microscopes, however, eyepieces are usually interchangeable. By switching the eyepiece, the user can adjust what is viewed. For instance, eyepieces will often be interchanged to increase or decrease the magnification of a telescope. Eyepieces also offer varying fields of view, and differing degrees of eye relief for the person who looks through them.
Modern research-grade telescopes do not use eyepieces. Instead, they have high-quality CCD sensors mounted at the focal point, and the images are viewed on a computer screen. Some amateur astronomers use their telescopes the same way, but direct optical viewing with eyepieces is still very common.
Click on the picture below for more information:
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Tele Vue Barlow Lens, 2x, 2" (Big Barlow) with Brass Clamp Rings. |
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Properly designed Barlows do wonderful things. First, they amplify power while retaining the eyepiece's eye-relief. Second, they slow the telescope's f/#, which improves eyepiece sharpness. Third, the designer can introduce compensations for eyepiece aberrations... |
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Celestron Accessory KitReviewsReally cool kit to enhace the real power of any mid-range telescope. Good quality lenses. Superb filters!...What else must I write?...Uhmmm...what are u waiting for?!!! you won't regret this purchase. The kit is overpriced. The 4mm eyepiece that comes with it is completely unusable. The eye relief (the space between your eye and the eyepiece) requires you to push your eyeball into the lens. As a matter of fact, nearly all of the eyepieces have horrible eye relief. The one I use most from the kit is the 9mm lens. You have to be pretty close to the opening in order to see anything. All of the eyepieces feel cheap. It seems like they're made in China - completely out of plastic. A few times, pulling the protective cover off of the 9mm, I felt as if I was going to break it. The barlow suffers from the same problem. It's cheap. But at least it's decent. Optically, it's alright. I could see paying $20 for one. The case everything comes in is actually really nice. It's well built, kind of tough, and has ample space in it. You could easily add a few more eyepieces. Of everything that came with the kit, I plan on holding on to the case for sure. I'm not sure of why or what I should use the filters for. After some reading of the instructions, I discovered I should use the lunar filter (it's blue) to take a picture of the moon with my cell phone. It cut down on the brightness but gave the moon a slight blue tinge. The picture I took looks like it's in grey scale. Before, the moon was way too bright to snap a picture of, so I guess that's one reason to use a filter. I tried out a few more and I don't think I liked them. I'm sure some people know how to use them, but I don't see myself getting much milage out of them for the time being. If I could do it over again, I'd probably only buy two or three really nice eye pieces. My 6se came with a 25mm. So then I'd get a 10mm X-Cel eyepiece (with more eye relief), a barlow lens, and maybe a wide field eyepiece from Celestron's Ultima LX series. An X-Cel 10mm lens costs $50, a better quality barlow will set you back $35. Already, you'd have a nice set of magnifications with real quality eyepieces that's 40-50 dollars less than the kit. You'll get tons more use out of just those two eyepieces (plus the lens included with your scope) than you will with the kit. I guarantee it. If you wanted to splurge, you could get a wide view eyepiece for $120. After viewing a few messier objects, I'm going to want one. In conclusion, skip the kit. Figure out which eyepiece you'll want by taking the focal length of your scope and dividing it by the eyepiece. For instance, my scope is a Celestron 6se. It's focal length is 1500mm. So, we find that with the included eyepiece, it has a magnification of 60x. With a 10mm eyepiece, you'll get 150x. With the barlow, you can get 120x and 300x (probably pushing it). You now have a good range of magnifications to see just about anything in the night's sky. If you choose to spend a little more and get a wide field lens as well, you'll be loving life. I'm fairly new to astronomy, but I expected better quality when I purchased this eyepiece kit from Celestron. After reading some of the reviews here, I was convinced that these were going to be some decent eyepieces and filters. This kit may be alright for some, but I found them lacking in quality of fit and build and would not recommend them to anyone who has the desire to use the high-power eyepieces (9x, 6x, 4x, etc). I bought these because of the low price tag, and for the most part, I regret not just buying one or two better quality eyepieces from Televue. The filters were really "cheap" too. Since I am a beginner I occasionally use this. But, I keep thinking of purchasing eyepieces of higher grades in the future. Optical qualites are fairly limited. The extreme small ones are too dark to use. It might be better to purchase 15mm and Barlow(sp?) lens seperately. You just can't beat the price! Wait they just did! I paid a little over 120 and they just dropped it 5. Great case. Eyepieces all work great and you get the filters also. Has extra room for your other eyepieces. I highly recommend this for all beginners like me, Average Rating:![]() |
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A good set of eyepieces will improve the performance of any telescope, and that's particularly true of entry-level telescopes that often come equipped with economy-grade eyepieces. The Celestron Eyepiece and Filter Kit includes five good-quality multicoated plossl eyepieces and a 2x Barlow lens... |
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Celestron 93230 8 to 24mm 1.25 Zoom EyepieceReviewsI purchased this for my Nexstar 6se based on the price and Celestron name. For general viewing this is a good zoom eye piece for the price. I used it to zoom into the moon and Saturn and both worked fairly well. One thing I noticed with this unit is that when you zoom you had to adjust your alignment on the object you were viewing and sometimes I had to refocus. I didn't mind those as the adjustment was not very much. The one thing I didn't like was the zoom control. I found it annoying at times to do the actual zoom with the way the zoom is setup. The zoom wasn't smooth and I often had to grab the eye piece with two hands with one hand to hold the eye piece and the other to turn the zoom. For me that was annoying so in the end I returned the eye piece and plan to instead look for a more refined piece rather then going for the cheaper Celestron. Un buen lente, para iniciar, te ayudara a aprender a encontrar objetos sin dificultades, aunque no tiene la mejor claridad lo recomiendo ampliamente para explorar el espacio. I bought one and it is fitting good for my Celestron 130 Astromaster. A little refocusing if move zoom in-out extremely. Image is sharp and clear, very confortable, large field of view. Personal, I like it. By the way, I saw the moons of Jupiter this year through zoom eyepiece ! I can saw also two colour bands of Jupiter, in town light polution. Jupiter scale like a pea. I bought this for my modest Meade 90mm refractor, and it works very well. I find it to be about as clear as the medicore stock Meade eyepieces I own. It will not be as good as premium eyepieces though. For the price, I think this zoom eyepiece was a good buy. It takes the place of several separate eyepieces. If you using a higher end telescope, you may want to look at a higher end zoom eyepiece such as the Baader Hyperion. Tried it on my first telescope - Celestron 80ED Spotter. Good and convenient. No need to change multiple eye pieces. Good buy. Average Rating:![]() |
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The Celestron 93230 8 to 24 millimeters 1.25 inch zoom eyepiece allows you to zoom instantly with your scope from 8x magnification to 24x magnification. |
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Celestron Collimation Eyepiece 1.25"ReviewsThis collimator is pretty fair, but I later ordered the laser collimator, and discovered that my main mirror was a little bit off. If you're on a tight budget, like I was, this will do a good enough job. Otherwise, get the laser! :) I'm still new at collimation. I use this to get the secondary mirror aligned and then use a laser collimator for the final adjustments. They seem to work well together. My laser collimator has a self-centering adapter to remove focuser slop. I wish this did also so I could be sure that they were "seeing" the same thing. It works fine. Takes a little getting used to it, but works like a charm. This is a great item for the "regular guy" in astronomy. Sure there are more expensive options (laser) but if you're collimating your dobsonian with a friend there is no easier/cheaper way than this tool. I've lined up my 8 inch dob with this tool multiple times and it never fails. Love this piece. Makes up an essential part of my dobsonian toolkit. This thing works. Right out of the box I was able to line up my mirrors in less that an hour to textbook perfect diffraction rings on a star. It is the first real collimation my scope has had since I got it. I bought a cheap Dobsonian over twenty years ago. Didn't use it much, had a couple of cheap eyepieces. It made pretty good images compared to other scopes but I was never sure of the collimation. Fast forward to today when the internet allows people to communicate with each other! Read the reviews on collimators and the articles on collimation. This device is a consistent favorite. Cheap and effective, it goes right to the front of my new and improved eyepiece collection. Average Rating:![]() |
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Celestron 1.25 inch (1-1/4 in.) Collimation Eyepiece |
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Vivitar Telescope with TripodReviewsThe telescope is very hard to work for children under 13. I was hoping to be able to set it up for my nephew, but it was hard for several grown people to try to focus the thing. My nephew said that the moon looked bigger if he just stared at it instead of looking inside of this thing. You know what they say, children always say the truth. I purchased this knowing I wanted a bottom of the line disposable product and I was not dissappointed. It is OK for the price as long as you immediately pitch the tripod into the nearest handy active valcano. You are much better off using your hands and a nearby tree or other support. Everything else works just fine for watching wildlife, but I would not expect it to do well for stargazing. a pair of binoculars works better than this telescope. It's really hard to find the target and does not bring clearer picture than binoculars. My 7 old son played with it two hours and has not touched for a few weeks. We'll see it can be used for birds watching. I purchased one at Walgreen's for $12.75 on close out merely as a demonstration for others of what not to buy. Sure, it is much better than what Galileo made, himself, 400 years ago, but: 1) The product is advertised on the box by the magnification it yields. The manufacturer is betting that you do not know that "quality" is based on light gathering ability (the diameter of the front lens, for a refractor telescope, or the diameter of the rear mirror, in a Newtonian reflector) and NOT by the magnifications printed on the box. 2) The mount is totally flimsy. The constant wobbling prevents clear viewing. A good mount should be able to dampen the vibrations after focusing, for example, in about 2 seconds. This one took about 15 seconds or more. And never stopped even with a light breeze. A solid camera tripod would improve the setup 10-fold. 3) The lowest power eyepiece (12mm/50x) exceeds the performance ability of the telescope for nighttime viewing. A general rule is that the maximum useful magnification = 25 x the diameter (in inches) of the lens (or mirror). The 2" lens x 25 = 50. 4) The eyepieces are poor. Only the very center of them appears to come to focus, with the rest of the image being blurry. And that's with daytime viewing. I can only imaging the collimation flaws in the optics when looking at stars. 5) The eyepieces are inferior, obsolete 0.965" barrel diameter. Today's eyepieces are a universal 1.25" (and 2" diameter for highest quality ones). 6) The box shows color images of the Orion nebula and the Pleiades. Color can only be achieved through time-exposure photography with the telescope on an equatorial mount. With VERY few exceptions (such as a 12" Newtonian reflector), color will NEVER be visible through an eyepiece on any telescope. When color is perceived, it is only when viewing the brightest emission nebula, and then the effect is a slight green color effect. If you are interested in a telescope, check out your local astronomy club for advice. Avoid any refractor less than 3" or any reflector less than 6 inches. I bought this for $20 at our local drugstore to use with my son. Once I got home and started to use it, though, I found the image was completely blurry and I couldn't see anything clearly... although I noticed objects directly in front of the lens were sharply in focus. After noticing about half of the reviews all across the Internet for this telescope were positive and half were negative, it occurred to me to check the objective lens (the big one at the end of the tube). Sure enough, once I unscrewed the piece that housed the lens and flipped it around, the telescope began functioning properly. I secured the housing back in place with some electrical tape. I think this solution should solve the problem for buyers experiencing the blurriness issue. Cheap materials (and apparently careless production) limit this telescope to young children or very casual astronomers. The eyepieces that come with the set are not terribly powerful (the moon will appear about the size of a dime) and I will try to locate some inexpensive upgrades. Luckily, the telescope has a screw attachment that will connect with a standard camera tripod, because the tripod that comes with the set is flimsy and not terribly useful for fine movements. In summary, I would recommend this telescope, with the caveat that you may need to do some fiddling to get it working properly and the magnification is not very powerful. However, the cheap price makes all of that palatable. Average Rating:![]() |
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From Vivitar. Telescope includes adjustable full-sized tripod, Mirrored diagonal eyepiece for easy viewing, Interchangeable 50x and 100x eyepiece lenses with storage cases, 3x finder scope to locate objects faster, Lightweight durable aluminum barrel, lens cap. |







