Porthole To The Sky for Less
Written: Dec 10 '05 (Updated Dec 11 '05)
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Product Rating:
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Pros: Easy to see through, inexpensive, sharp image, usable in daylight.
Cons: No included lens caps.
The Bottom Line: This eyepiece performs very well with a nice wide and sharp image. For a telescope with a large focuser, it presents a beautiful and easy to see image.
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| Pirich's Full Review: Celestron 32mm E-Lux Plossl Eyepiece (93335) |
The E-Lux 32mm eyepiece is a designed to produce wide fields of view of the night sky. The 2" diameter body allows the field of view to be larger than would be possible with smaller 1.25" diameter eyepieces. It is an economical and effective way to get a much more comfortable wide field view in a telescope with a 2" or larger focuser.
Description
The 2" size eyepieces were developed to obtain wider actual fields of view than the more common 1.25" diameter telescope eyepieces allow. The housing and eyepiece proportions are all scaled up, resulting in what looks like an XXL version of a telescope eyepiece with greatly increased weight. They can only be used in telescopes able to send such a wide light path to the eyepiece. This is usually a feature of telescopes with larger 2" or bigger focusers designed for photography with large format cameras (or schmidt cassegrains).
The E-Lux eyepiece is very solidly built and yet has a very soft rubber light shield around the eyepiece. The wide lenses are coated, so internal reflections are minimized. The main body has a rubberized grip built into it. The inside of the eyepiece body is blackened to minimize glare. The nicely-chromed collar for the draw tube has a notch in it to catch set screws and prevent the eyepiece from falling out.
The only complaint I have in this department is the eyepiece does not come with either a top or a bottom lens cap. As a result, I have been leaving it in a telescope with the ziplock bag it came in on it. I have been looking for at least a top end plastic cap for it. So far I haven't found a part with a reasonable fit.
Performance
The E-Lux 32mm 2" eyepiece can be most easily understood in comparison with Celestron's 32mm 1.25" Plossl eyepiece. The two have the same focal length, and the overall body of the 32mm eyepiece is as long. However, the barrel is much smaller on the 1.25" size. Since I had both, I have given them both a trial. I have been using the 32mm E-lux in the Celestron 80ED f/7.5 refractor, and its performance has been such that it is the eyepiece I leave in it at all times.
The difference between the two eyepieces tells why 2" size hardware exists. The 32mm 1.25" eyepiece has a 46 degree apparent field of view, which is limited by the diameter of the 1.25" collar. This gives a bright image, and the image is projected well away from the eyepiece, but the scale is limited. In comparison, the E-Lux eyepiece is a 56 degree apparent field of view. It doesn't sound like that big a difference, but approaching the telescope shows a completely different appearance. Instead of having the feeling of going to peer through a small hole, this eyepiece gives the feeling of looking trough a porthole. It's the difference between looking through a knothole in a fence and looking over it. The image is projected so far from the eyepiece and the field is so wide, looking into it is effortless. The actual magnification with these lenses was 18.75 power with an actual field of view just under 3 degree across (large by astronomical standards).
The E-Lux design has three lenses inside, so many would claim it is theoretically limited in its ability for color correction. In practice, this is not the case, and the field, though slightly curved (slightly fisheyed), comes into sharp focus from edge to edge. It is only able to show some false color on the edge of the moon if you move the moon all the way to the edge of the field of view. Here, the interior side of the moon will show a razor thin red edge, and the exterior side will show a similar sized violet edge. Since the telescope is a refractor, this may be more from its optics than the eyepiece. In actual use, this is so difficult to see, I doubt a visual observer would find reason to complain.
In astronomical use, star clusters such as Double Cluster and the Plieades show their stars as bright pinpoints and present a beautiful 'Diamonds on velvet" appearance. Nebulas such as the Orion Nebula can easily be seen in their entirety, but need a dark sky site out in the middle of nowhere.
As a secondary test, I put this eyepiece into an 18" f/5 dobsonian telescope belonging to a friend and found it was now possible to see the entire double cluster, which was not possible with the 17mm Televue Nagler he had been using, despite its 70 degree apparent field of view. The simple E-Lux design held up surprisingly well with this competition, and worked well with this very different telescope. The resulting image was extremely bright and sharp, and made extended objects visible.
When pointed at objects on the ground, the 32mm E-Lux eyepiece gives nice wide razor sharp images. As a case in point, a few weeks ago I was outside during the day and two air force planes flew over (Tucson is cool). I looked up at them as they went by overhead, and saw to my surprise they flew in front of a tiny pinpoint of light visible in the middle of the day. I thought at first I might be seeing a satellite, but the object appeared nearly stationary. On the chance it would be there, I went in and quickly brought out the 80ED with the 32mm eyepiece mounted in it. I pointed it at the object and took a look. It turned out to be four yellow children's balloons tied together with what appeared to be an orange note attached (someone out there has sent a message on a balloon...).
Conclusion
The E-Lux 32mm 2" diameter eyepiece is an economical way to get very wide angle performance from any telescope with a large focuser. The eyepiece is flexible for day or night use, and gives a very bright and sharp image across its field of view. Although higher performance and wider field eyepieces are available, this one does what it does very well for what it costs, and that is the true sign of value. In comparison to its 1.25" diameter cousin, its performance is obviously more pleasing. Its biggest fault is the lack of included lens caps, which would have been a trivial expense for Celestron to correct.
Recommended:
Yes
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Epinions.com ID:
Pirich
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 in Electronics |
 - Top 500 |
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Member: Rich W.
Location: Tucson, AZ
Reviews written: 137
Trusted by: 40 members
About Me:
Dad, Engineer, Scientist, Astronomer, Traveler; order may vary.
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