sandokan said:
Vixen 6 is too soft and I'm selling it, 12.5mm offers an excellent view due to the relative low mag (31x) and the Vixen 9mm is on the edge of quality. Unfortunatelly the view through the 9 is lower quality than the 12.5, i.e. it is softer. I don't know is this due to the EP or the optical limit of the scope is reached at this mag (43x) ?
I don't think it's the ep, it's the magnification. As SF indicated above, when you increase magnification you lose brightness. You can't change how much light comes through the objective lens of the scope, so you're spreading the same amount of light thinner and thinner when you increase magnification. Also, as you zoom in, eventually you'll start losing resolution -- in other words, the pitcture is getting bigger but not more detailed. Going from the 12.5mm to the 9mm is a 39% increase in magnification, which is a pretty big step.
sandokan said:
I am on the way to find some other 10 or 9mm EP, which will give the same level of quality as the 12.5 or longer EPs.
The eyerelief is not important, I can accept from everything from 13-20mm. I don't need wide ep, 60deg is enought. But I would like to get good sharpness and contrast. I think that I should buy some more $ ep, like the televue radian or pentax XW ?
I would like to ask you have you made some tests with the Pentax 65 equipped with the top EPs of 9 or 10 mm (televue, XW, XL)?
Can I get the better with them comparable with my current Vixen LV9 ?
Can I expect a better view with the Pentax XF 8.5, is it ''better'' than LV9 ?
Can I expect the TMB 9mm will give sharper view than the LV9 ?
SF seems to have found that the simpler design of the TMB will outperform the complex 7- or 8-element designs of the WFs like XW, XL, Stratus. I think he makes a very good point that when you want that high magnification, you're not going to be scanning around, you're probably trying to get a little bit "closer" to that faraway bird to make the difficult ID. In this case, the brightness, contrast, and resolution on-axis (i.e. in the middle) is the most important thing.
I'm definitely going to give that 9mm TMB a try and put it up against the 10.5 XL for long-distance ID's.
I can tell you about my experience with the XF 12, and my recently purchased (used) XL 14 and XL 10.5. The XF isn't any less complex than the XL/XW, it's just smaller and doesn't use the high-end lanthanum glass. And my personal experience so far is that the XL's are just superior eyepieces to the XF's.
The difference in AFOV isn't that big (65 vs. 60), but the XL's are obviously brighter and maintain their crispness from edge-to-edge. I didn't notice it as much before I got the XL's, but the XF12 eyepiece starts to lose a lot of image quality on the outer 20% or so of the field. The quality in the middle is pretty close, but when I'm scanning a flock of shorebirds, being able to have the peeps on the edge of the field still be crisp and identifiable is a nice plus.
The amazing thing is that the XL 10.5 doesn't seem any less bright than the XF 12 (though it's only about a 14% increase in magnification), and it also beats the XF 12 in edge-sharpness. But, even the 10.5 (at 37X magnification) doesn't help when I'm looking at something far away and the heat waves are shimmering. In other words, sometimes it's the atmospheric conditions that are the limiting factor, and the magnification only makes it worse.
But if the conditions are nice and I'm not looking at something that's a zillion miles away, both the XF 12 and the XL 10.5 allow for nice, closer study of ducks and shorebirds at medium-to-long ranges.
I felt that the XL14, at 28X, was just about the sweet spot for the PF-65. Everything was bright and crisp, I wasn't pushing the limits of the scope at all, and the 65-degree widefield view was beautiful for scanning mudflats. I personally didn't have the problems that SF did trying to find the "sweet spot" when viewing -- once you get the eyecup screwed out to the right distance for the eye relief, I found it very pleasing to look through. The XW is supposed to be the same (or a teeny bit better) in image quality, with a 70-degree AFOV. I would imagine an XW14 paired with the PF-65 would be a fantastic combo for almost any situation.
As to some of your other ep questions, I'll relate what I've read:
From my reading, the Vixen ep's in general (LV and LVW) are very highly rated, and I doubt you'll see an improvement going to the XF. I also read a technical review of the TV Radian 12mm vs. the XF 12mm, and it was basically a tie. I think that the Radian, XF, and LV are all very comparable, and the difference between them is largely personal preference.
I think that the Pentax XW/XL (considered to be among the finest ep's out there) are a definite step up in overall quality -- but not in a way that is necessarily going to allow you to comfortably have 50X magnification on a small scope like the PF-65. Pentax XW's are most often compared to Naglers and Panoptics, but I don't know if those are as suitable for birding (way less eyerelief).
Vixen LVW's (from which the Orion Stratus and Baader Hyperions are cloned) get extremely good reviews, and the LVW or Stratus are pretty much the consensus "best-bang-for-the-buck" widefield ep's. I actually thought the Stratus 13mm was better than the Pentax XF 12, but I couldn't zip the PF-65 case closed with the Stratus attached.
Anyway, that's all very long winded, but here's some brief suggestions:
1. The classifieds at
www.astromart.com are a great place to buy/sell eyepieces.
2. Before you spring $300 for a shiny new XW, try out other options like Stratus 8mm or TMB 9mm. You could spend less than $200, buy a couple of different used ep's, and then keep the one you like the best. Keep your eye on the classifieds at astromart and you might find a used option at a good price.
3. I would sell your LV 6 (way to powerful for the PF-65), but maybe hang onto the LV 9 for now and see for yourself how it stacks up to other options. You can always sell it later if you like something else better.
4. The bottom line is that you have to see what works for you -- ep's are very much a personal preference. And, again, with quality ep's you can always recoup 70-80% of your money selling them used on astromart or eBay. These astronomy guys have collections of 5-10 or more ep's and they like to swap and sell and try different ones out.
Hope this helps!