Not Quite Like Anything Else From Celestron
Written: Apr 01 '07 (Updated Apr 08 '07)
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Product Rating:
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Pros: Compact, good optics, beautiful fit and finish.
Cons: High cost relative to C80ED, Crayford Focuser Creep.
The Bottom Line: The Onyx 80ED is a beautiful and functional telescope. It seems slightly expensive for what it does, but not outrageously so.
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| Pirich's Full Review: Celestron Onyx 80EDF (150 x 80mm) Telescope |
This may be the most aesthetically pleasing piece of hardware ever to come out of Celestron. The entire telescope is polished, and either liquid gloss black, metallic orange, or chrome on the various knobs. And, compared to its size, it is one of the more expensive scopes Celestron has put out in this size. It performs very well optically, and is mechanically superb otherwise. More general information on choosing telescopes can be found in my article on Picking a Telescope.
Background
The Onyx 80ED is an unexpected follow-on to the excellent 80ED APO Refractor. Where the optics in the first 80ED are an f/7.5 prescription with a 600mm focal length, this version has a shorter focal length at 500mm and f/6.25.
These telescopes are part of a seeming sea-change in the telescope market as very capable telescope systems which previously were only available as specialty products at extremely high prices from companies like Takahashi and Tele Vue.
The new player in this, no joke, is not making themselves directly visible, but seems to be a real life shadowy organization. It appears to be a house in Taiwan, perhaps Synta, has started making high end refractors, and is either directly or indirectly involved in the actual hardware showing up in brands such as Stellar Vue, Celestron, Orion, Astronomy Technologies, and perhaps William Optics. And, if you look up Synta (who now owns Celestron) on the web, you may conclude they simply do not exist.
Classically, the problem of making a telescope has oscillated between the problems of refractors, with their false color problem caused by the nature of light where different colors bend different amounts when they move between materials, and reflectors, and their peculiar problems with secondary mirrors and the difficulty of making a perfect mirror geometry.
The solution at a reasonable cost has been the Achromatic refractor, which used two types of relatively inexpensive glass to make a compound lens at the front end to get better color correction, and still have some false color. At very high cost, high end refractors such as the Televue 101. These extremes are a large part of the driver behind other telescope designs as it has been possible to put together fairly extraordinary performance within the cost of an equivalent apochromatic refractor.
It was the original 80ED which signaled this may be changing. Two variants, one from Orion and one from Celestron appeared with the same optical prescription, and appeared to have the same actual optical cell in the front, but the rest of the optical tubes was unrelated. Following these have been a full stable of similar scopes in 100mm and 120mm diameters. The mechanical elements of these telescopes were still closely related to the older short-tube series scopes like the Wide View 80.
In the 2006, the more interesting step of the optical tubes catching up with the exotic glass appearing in them. Several different variations showed up at about the same time in the form of the AT-66ED and the same telescope sold by StellarVue, this telescope, and another Astronomy technologies scope in 80mm size, but with a longer focal length. Strangest of all, all of these have mechanical or other features in common. Confused by all of this? Hey, it's a real life mystery.
Description and Usage
The Onyx 80ED is in production and up for sale as the Celestron 80ED APO refractor. Because of this, it seems only natural for the two of these to get compared, expecially since there needs to be some justification for the Onyx to sell for $180 more than the 80ED.
The main difference between the Celestron C80ED is how they are built. The original scope is built more like a piece of military hardware with a thick coat of paint, heavy duty parts, and a rugged rack and pinion focuser. The new Onyx 80ED is much more refined with a retracting dew/glare shield and a smooth all-rolling Crayford friction based focuser.
The entire back end of the telescope is free to rotate with a small set screw on the top to stop it in position. This is a feature which is only really useful for photography, where it lets you get the photo oriented more easily than trying to rotate the camera in the end of the focuser. The telescope has a set of chrome focus knobs for the Crayford focuser, which uses a smooth set of rollers instead of a spur gear engaging a rack as in the C80ED. This type of focuser has been popular recently since there is no feeling of the subtle bumps of the pinion moving by as in the other type of focuser. The down side with a Crayford is since there is no direct mechanical engagement and it only uses friction to hold on to the draw tube, the focuser will tend to slide when the telescope is elevated, and the Crayford roller may slip rather than drive the draw tube forward. This is precisely how the Onyx 80 behaved when I put it near the zenith to look at Saturn.
As in the smaller AT-66ED, there is a knob below the focuser to lock the draw tube in place. As mentioned in my review of the AT-66ED, my scope was missing this part when it arrived. Since I got to see the replacement, I decided to pull the focus lock on the 80ED and see if it was the same part. The chrome knob had the same type of knurling on it, and had the same plastic insert on its end to not mar the draw tube. It really looks like the same part. The focuser in this scope does not have a fine slow speed knob on one side, so there are differences there, and this draw tube has no measurement scale to be able to reproduce focus. The larger 2" diameter means this scope can directly accept 2" size eypieces and diagonals, so it is well suited to wide-field viewing.
The telescope has a mounting foot similar to the AT-66ED, which is sufficient for mounting on a photo tripod. If the telescope is to be mounted for astronomical use, I suggest getting Vixen-compatible dovetail stock from Orion at www.telescope.com to let this mount on a CG-5 or other convenient mount and balance with a camera installed.
In terms of similarities to the AT-66ED, the telescope has the same all-polished look, with very tightly fitting components. It does have one feature none of the Astronomy Technologies scopes have- a small peep-sight on the left side of the tube. This is perhaps the most peculiar feature on this telescope since it's so small and close to the barrel, it is very hard to use, and at the same time it breaks up the otherwise smooth outer form. I found aiming along the barrel worked fairly well for aiming it. Since it only has a vestigial mounting block, but does have a rotating focuser, you will likely want to adapt it to a Vixen type dovetail to put it on a mount. Dovetail bars are available from Orion (www.telescope.com- search on Dovetail) and more detail is in my review of the Orion Dovetail.
Optically, this telescope is unique among all of the current crop of small doublet refractors with a focal ratio of f/6.25" at 80mm. In comparison, the f/6.8 of the larger Astronomy Technologies scope and the f/7.5 of the C80ED cause these scopes to have smaller fields of view and dimmer images. When we went looking for false color on the edge of the moon, none was found that could not be attributed to the inexpensive eyepiece and prism diagonal since they disappeared with a mirror diagonal and nicer eyepiece. On the bright white star Sirius, the image showed a tiny amount of purple. On the Plieades star cluster, this telescope recorded the beautiful diamonds on velvet look of the new blue-white stars. In comparison, the C80ED has no appreciable color, either. The main trick here is getting a wider field of view and brighter image.
Conclusion
The Onyx 80ED is a flat-out beautiful telescope. It really has the look and feel of something intended for advanced amateurs, and since it has no mount with it, it is really an a la carte type of astronomical purchase. The price at just under $700 is a bit over twice what the AT-66ED cost from www.astronomics.com. On the other hand, this may be the best 80mm doublet scope currently available. Given the issues with Crayford focusers, I personally prefer the rack and pinion the older C80ED has, though some work can get it to be tighter. The focal ratio is not currently a do-or-die for me since the AT-66ED I have is a little faster at f/6, and a Schmidt Cassegrain gets near this ratio at f/6.3 when the focal reducer is used. Given the only flaw I found in the scope is the silly peep-sight, it looks to be a solid purchase for a telescope one could expect to use for many years.
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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