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Originally Posted by janoskiss
Keep in mind that every subjective qualitative review is based on personal opinion. Are you aware that the co-author of Iceman's review, John (ausastronomer) puts the Pentax on top?.
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CJ- A couple of things you need to understand. The same make and design of eyepiece will not perform at the same level in all focal lengths, this is because some focal length ranges hit the sweet spot and all eyepieces have compromises (left in) to some extent. No eyepiece is perfect, irrespective of how much money you plan to spend. The 14mm Pentax XW is not the best of the XW series, that claim belongs to the shorter focal lengths (5mm,7mm and 10mm), however it is still an exceptionally good eyepiece. It depends on what aspects of an eyepiece's performance are important to you, as to how you rate its performance level. Mike liked the 13mm Nagler because he was "spellbound" by the fact that it gave a sharp view across the entire 82 deg FOV, whereas the Pentax didn't. In terms of the EOF performance of the 14mm Pentax XW, it is not bad, stars do not become off-axis "astigmatic slits" like they do in cheap eyepieces. In the outer 20% of the FOV the stars stay perfectly round but "bloat" in size by about 5% as they are just off best focus due to a little field curvature. This is detectable when you do a direct A/B comparison against the Nagler but it is minimal when you just use the 14mm Pentax in isolation. The 14mm Pentax is certainly usable right to the edge of the 70 deg AFOV. The off axis field curvture in the 14mm Pentax is not detectable on diffuse objects. In terms of eye-relief and comfort the Nagler is not useable with glasses on, but is quite comfortable without them, it has about 12mm of eye-relief. The Pentax has 20mm of eye-relief and also has an adjustable screw up/down eye guard, it is perfectly usable with or without glasses on. There are several aspects of eyepiece optical performance where the 14mm Pentax is superior to the Nagler. The Pentax is sharper on axis and has higher light transmission. I also think it has slightly better contrast and cooler more neutral colour tones. The Pentax has no distortion whereas the nagler has distortion left in the design to allow a flat field of view to the EOF. This rectilinear distortion is not really detectable when vieing astronomical targets at night (unless you know what to look for), but is detectable when panning the sky in a dob at night or when using the eyepiece during the daytime in a refractor for terrestrial viewing. Two of many tests we conducted as part of the review was on 47 Tucanae (NGC 104) and on the multiple star HN 40 in the middle of M20 (Triffid nebula). Mike felt the performance of the 14mm Pentax on 47 Tuc was inferior to the other eyepieces because the cluster "appeared" less resolved. This was because the Pentax had higher light transmission showing many of the 14th magnitude cluster members, which were not showing in the other eyepieces, making the field more congested with stars and appearing less resolved. On HN 40 the "d" star was visible with direct vision in the 14mm Pentax, it was visible with averted vision only in the 13mm Nagler T6 and it was not visible at all in the 14mm Series 4000 Meade UWA.
Ultimately at the top end of the tree, which is where you're at with Pentax XW's and Nagler T6's, they are both outstanding performers and each will outperform the other in certain areas, it depends on the areas that are important to you. In addition, its worth noting most of these differences are fairly minimal and it takes very good conditions and an experienced eye/observer to detect them. For what its worth IMO the 14mm Pentax XW is at least the equal of the 13mm Nagler T6 because it excels in the things that are important to me. Namely, on axis sharpness, light transmission, contrast and comfort.
Whichever of the two eyepieces you chose at this level, you would ultimately be a happy camper.
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Originally Posted by janoskiss
I can thoroughly recommend the 13mm Orion Stratus. I did have both a 13mm Stratus and a 13mm T6 Nagler, and spent many hours comparing them.
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The above all having been said, I used Rod Berry's 17mm Orion Stratus last Saturday night at Kulnurra, albeit for a very short time only due to cloud, in my 10" F5 dob and was thoroughly impressed (or was it the Tooheys affecting my vision ?
). This was my first opportunity to try this eyepiece and I have to conclude that for $180 it represents truly outstanding value. Not quite as good as the Nagler T6 to the EOF but certainly good to the EOF in an F5 scope and very good on axis performance. It really was a great performer considering its price. If money is a concern to you in any way, the 13mm Orion Stratus for $180 is clearly your best option, it has 90% (or a little more), of the performance of the premium eyepieces at 40% of the price.
The 13mm Vixen LVW that you were also considering is another superb eyepiece, it offers 95% of the performance of the Nagler and Pentax and is about $100 cheaper, so don't rule it out either particularly on AFOV alone.
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Originally Posted by janoskiss
Have you looked through one? 65degrees is generous IMO. 70 is the most I would ever want.
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I agree with Steve here, a 65 deg to 70 deg AFOV is plenty for me and I find it just as engrossing as the 82 deg AFOV of the Naglers. Some observers find that little bit extra AFOV of the Naglers worthwhile, not me, too much information for my small brain to process
CS-John B