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Agena 1.25" ED Eyepiece - 5.2mm

5.0 (1 Reviews) Read Reviews Write Review
Brand Agena AstroProducts
Part Number -

Product Info

Manufacturer Description

ED stands for "Extra-Low Dispersion". These eyepieces use optical glass in which two of the lens elements are crafted from ED glass which is a special grade of glass that provides much superior refractive properties as compared to standard optical glass. This results in much better color correction. ED glass is often the type used in many expensive camera lenses and high-end refractor telescopes costing thousands of dollars.

Our ED-series eyepieces are available in a 1.25" barrel in 10 focal lengths (2.3, 3.8, 5.2, 7.5, 9.5, 12.5, 14, 18, 21 and 25mm). They feature a six-element lens design that provides significantly reduced chromatic aberration, high resolution and excellent sharpness without compromising image brightness. Their long 20mm eye relief means that even eyeglass wearers can take in the full 55-degree apparent wide field of view (AFOV).

All ED-series eyepieces are fully broadband multi-coated for maximum image brightness. Lens edges are blackened throughout for improved contrast. The eyepiece housing is precision machined from aluminum and clear-anodized to a lustrous finish. A rubber traction ring ensures a secure grip and a rubber eyeguard helps position your eye to block out stray light. The chrome barrel features a setscrew recess for added security. All eyepieces are parfocal and are threaded to accept standard 1.25" filters. Each eyepiece comes in a bolt case with two plastic end caps. Compare these with the ED eyepieces sold in very similar focal lengths by two of the "Big-3" telescope companies and you'll realize the savings we offer.

Important note: Depending on your telescope, this eyepiece may provide magnifications that are too high! While it can be very useful for viewing the Sun, Moon, brighter planets and terrestrial objects, it is not for everyone or for common viewing conditions.

Before buying, please make sure that you are using realistic magnifications with your telescope. A good rule of thumb is that under very good conditions and with a very good telescope, the maximum power you will be able to use is about 50x of magnification per inch of telescope aperture. With average telescopes and/or average conditions, you might be limited to 30x of magnification per inch of telescope aperture. So for example, if you have a 4" telescope, under typical conditions you might typically use 4x30 = 120x of magnification, and 4x50 = 200x of magnification at best. If your telescope has a focal length of, say, 1200mm, then this eyepiece will result in a magnification of 1200 / 5.2 = 231x which is probably too much for this telescope.

Also, when you magnify an object, its light is spread over a larger area. Since the brightness of the object being viewed hasn't changed, this means that the image you see will be fainter. Double the magnification and the image will get 4 times fainter. This is a basic law of physics, but people often forget this and complain that the "image is not bright enough" when they increase the magnification to very high powers.

Boosting the magnification beyond the recommended maximum for your telescope aperture is not realistic. This is bound to result in image break-down, causing faint, fuzzy images, focusing difficulties, increased color around objects and general disappointment. Use the eyepiece in the right settings and with the correct expectations, and you will enjoy it.


5.0 (Based on 1 Reviews) 100% of reviewers recommended this product.
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    1. AstroGuy1

      AstroGuy1 New Member

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      User Notes:
      Review by Joel of Colorado.
      Nov 22, 2008

      5.0 Great Eyepiece


      Lightweight,Crisp sharp images,Low price




      I just got back from my observing session with this eyepiece. I viewed through an Orion XT8 Classic Dobsonian. Because of poor weather, I only got a chance to look at the Orion nebula and the Moon. I had excellent views of the Trapezium and clearly discernible nebulosity, in spite of light pollution and some cloud obscuration. The Moon was unbelievable. Amazingly crisp and sharp images. Used the 2x Barlow with it and it was still pretty good, but this took me to 560x, way past the theoretical max magnification for my scope. I highly recommend this EP.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

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      Apparent Field of View 55°
      Barrel Size 1.25" (31.7mm)
      Bolt Case Included Yes - Manufacturer Supplied
      Bolt Case Size -
      Coatings Fully Broadband Multi-Coated
      Height (with Eye Guard) 4.8" (122mm)
      End Caps 2
      Eye Relief by Design 20mm
      Filter Threads Standard 1.25" Filter Thread (M28.5 x 0.6)
      Focal Length 5.20mm
      Lens Elements 6
      Rubber Eye Guard Yes
      Blackened Lens Edges Yes
      Manufacturer Agena AstroProducts
      Eyepiece Focal Length 5.1mm - 10mm
      Eyepiece Field of View 51 - 60 degrees
      Eyepiece Series Agena ED
      Barrel Type With safety undercut
      Eyepiece Weight 7.20oz (204.12g)