Posts Made By: Mike Hosea

One thing about these eyepieces, and the new Antares 70 degree models is that they are employing some kind of coating technology designed to LOOK like good multi-coatings without actually BEING good multi-coatings. These are pretty coatings that look green from some angles and blue from others. People who don't know what to look for will then note that the coatings look very good, but in fact they are horribly inefficient, probably far less efficient than single-layer MgFl2 coatings. When I look almost straight down at these coatings, I get the green reflection where I should be getting blue, and the reflection is bright enough to shave with. Holding one up side-by-side to a Tele Vue 20mm Plossl shows just how bad it is, despite how pretty they look.

Here's a photo of a cheap Russian binocular eyepiece, a 20mm TV Plossl, and a 5.7mm Antares W70. As I recall, the coatings on Expanse-type eyepieces were similar in nature. Note that the camera is directly above the midpoint between the 20mm Plossl and the Antares W70, and the lens surfaces are at the same height. I tried various camera positions with similar results.
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Mike

I've done the same to my Antares 5.7mm W70. This may help some with lunar and terrestrial performance, any context where there is a significant amount of bright target area outside the field of view, in which case it is possible that light may bounce off the walls and back into the light path. I think it will do little or nothing with respect to ghosting from planets that fit entirely within the field, although deep sky views may gain a small amount of contrast.

I also discovered that my eyepiece had a fairly un-blackened spacer ring in the upper assembly. Blackening that seemed to make a major improvement in glare from a bright object just outside the view. Nothing I have done has made it a great lunar eyepiece, however. It's sharp, but there is just too much light bouncing around in there, I think because of the coatings. On the other hand, I think it does well with Jupiter and Saturn.
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Mike

Yes, Chris is correct, although my recollection from testing years ago was a range of 2.1x to 2.4x, with an average probably around 2.2x, depending on spacing to the field stop of the eyepiece. The only half-way reasonable workaround I can think of is to find a way to move the Barlow lenses closer to the CCD chip, perhaps by unscrewing the silver barrel from the black eyepiece holder and instead of the black eyepiece holder using a section of 1.25" ID pipe with set screws at each end that will allow you to control the spacing between the chip and the Barlow lenses.
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Mike

Somebody experienced with eyepieces at all quality levels needs to be loaned a set of each and given an opportunity to check them out and compare them. It's hard to get anywhere with just a few trials. I bought a 20mm Expanse type and a 5.7mm Antares W70, and I'm already tired of actually BUYING these eyepieces, at least at full price.

Anyway, I know that in the years past there were inexpensive Plossls that compared well to the expensive ones and inexpensive Plossls that did not do as well. Stands to reason that the same would be true of these new offerings of more complicated designs that sport long eye relief and wider apparent fields of view.

What I'd like to home in on in this LER and SWA category of inexpensive eyepieces are the moral equivalents of Celestron's old Plossl line as they compared to higher quality Plossls. They didn't perform as well as the Ultimas or Tele Vue's, but for the most part they performed without making themselves conspicuously inferior in any particular way.
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Mike

I don't know what was going on with your 12mm Radian. Despite Tele Vue's 100% QC practice, defects do slip through. The 7mm Nagler Type 6 that I have had a warranty repair (came with a scratch at the edge of one of the internal lenses), and the 5mm Nagler Type 6 was a replacement of the one I bought new because the latter had serious optical problems.

Another possibility (besides a defect) is that you were moving your eye around in the exit pupil too much. This will cause slight color fringing around objects anywhere in the view, not just lateral color at the edge (in fact the technique of eye placement in the exit pupil can be used to partially null out lateral color at a given point in the view). You might need to use the pupil guide for awhile to train your eye for the eyepiece if that is the problem.

Anyway, I've owned all of them except for the 6mm. I've only used the 6mm briefly but saw nothing unexpected, and I've used the others fairly extensively. I have NEVER seen an internal reflection in a Radian, only external reflections off the eyeball, to the eye lens, and back to the eye. Unfortunately, I get that with all wide-angle long-eye relief eyepieces, ALL of them, and I noticed that effect first with a Plossl in a Barlow (looking at Jupiter, naturally).

Radians do have some LATERAL color, but so do all other super wide angle eyepieces I've seen, although some have more than others. Performance of the Radians is more or less uniformly on a par with a high quality Plossl in a good Barlow, with an extra 10 degrees of field, of course. In my old MK-66 Deluxe, I got better planetary performance out of an 8mm Radian than anything else I tried in that scope.

Radians are sold on Astromart at a steady pace and have been for years now. If anything, I see fewer of them for sale lately.

I own no Radians now, however. I prefer the Type 6 Naglers.
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Mike

Looks nice, but $300--ouch! I think they're flirting with the top of their niche there.
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Mike

Are you sure about 5% reflectance with low-angle specular reflections off a smooth flat black painted surface?

Biggest bang for the buck, though is opposite the focuser. Light reflected off the tube opposite the focuser can have straight shot into the eyepiece, and beyond the tube (if it is too short, as they usually are if the focuser is low-profile) light can come in without even a reflection and get inside the eyepiece. It usually doesn't have a straight shot to the focal plane inside the field stop of the eyepiece, but it can show up outside the exit pupil and cause a glare problem.

As for baffling the rest of the tube, many choose not to, but there is scatter to think of as well. Some of the light striking the tube wall will reflect in specular fashion, but some of it will be scattered. When this happens all over the tube I think the results can add up to something noticeable at the eyepiece, but as I said before, baffling opposite the focuser is priority 1.

BTW, check out the reflection of the tube near the fan in the mirror box from this angle in the photo below. It's painted textured black like the struts everywhere else. Of course this angle isn't relevant in this scope (and the shroud would normally be up), but notice how bright the reflection is off that short section of tubing.
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Mike

Yes, all Radians and to my knowledge all of the Panoptics and Naglers except for the Type 6's and Zooms are made in Taiwan. FWIW, I think this source's QC is pretty good, and I'd have a hard time believing the Japanese factory is better, given that the two defects I've ever seen in Tele Vue eyepieces came from the Japanese source, not the Taiwanese source. Besides, times change. Take care that general notions of where high quality is produced do not become outdated. Cheap eyepieces have been "cost-reduced" to the PRC by now. It's hard to find a cheap eyepiece that is made in Taiwan anymore. For awhile Meade Stupor Plossls (I just like to poke at Meade for copying Tele Vue and making grandiose claims) and inexpensive Celestron Plossls were coming from ROC, but that is a thing of the past.
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Mike

Like zis?

http://www.cloudynights.com/eyepieces/pentax40.htm

Either should be fabulous in a C8. The XL is a lot lighter and gives nearly the widest true field of view you can get in a 2" focuser. The 35mm Panoptic should be sharper at the edge of field, and the magnification will obviously be a little bit higher, which may or may not be important at your observing location. I recently had to abandon 40mm eyepieces entirely at my viewing location after realizing that I could pan over M1 without seeing it at that magnification. Didn't used to be that way, but this was an f/5 Newt. Giving up 40mm eyepieces for me is like you giving up 80mm eyepieces.
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Mike

I would agree with the sentiment that a 1.25" Barlow is what most people need. Some people Barlow 2" eyepieces, but in a star diagonal this is mechanically troublesome, and it adds unnecessary weight to small and medium size telescopes. Seems to make some sense with big Newts, though, where the Barlow can be inserted to its parfocal point and the weight is not an issue.

Rather than Barlow their big 2" eyepieces with a 2" Barlow, most people would be better served by a careful selection of 1.25" eyepieces and possibly a Barlow or Powermate.

The 1.25" Tele Vue Barlow is an excellent choice. You'll have to check with your 2" diag whether it will contact the mirror. It probably won't, but if it does you can put some slipjoint washers on the barrel or buy a Tele Vue high-hat 1.25" adapter. Either will solve the problem. The only less expensiver model that I would half-way recommend is the 2x Celestron Ultima or one of the equivalent models, like the Orion Shorty Plus. IMO, the 2x Tele Vue Barlow is better and not much more expensive when purchased used on Astromart. If you buy it new, you should be assured of getting a compression-ring type with captive thumbscrew.

Another solution is a 1.25" 2.5x Powermate. That unit will work better than a Barlow with Plossls. The reason is that regular Barlows may cause some vignetting (the apparent field of view is reduced, sometimes significantly, e.g. from 50 degrees down to 40 degrees) and increase the eye relief noticeably in longer focal-length Plossls. The 2.5x Powermate will eliminate or minimize both these failings of ordinary Barlows, so it's well worth considering, but unfortunately, a 1.25" 2.5x Powermate costs $190+ new, which is rather steep.
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Mike