Lehel said:
Hi All,
I would ask you what are your opinion with these eyepieces!
I have a PF80 with XW14 and I would like an eyepiece with shorter focal length.
Thanks in advance
Lehel
I can't compare the XF8.5 to the XW7, but I had both the XL10.5 and the XF12 and the XL is simply the superior EP. The XW's are the replacement for the XL, with a wider FOV of 70 degrees (vs. 65 for the XL) and maybe a little better contrast and transmission.
The increased field-of-view is a nice plus. I'll leave the back-of-the-envelope calculations to those who know the math of astro-ep's, but I'd be willing to bet that the XW7 at 70-deg. will have an equal or greater actual FOV to the XF8.5 at 60-deg. So you'll see the same amount of stuff but at higher magnification.
Additionally, the XL10.5 was as bright than the XF12, even though it was higher mag. The view, to me, was simply much more pleasing through the XL.
The XL (and I'm assuming the XW's also) stays sharp and bright right out to the edge. It's nice to be panning a flock of shorebirds and be able to easily ID the guy that walks in at the edge of the field. There is a little bit of CA when looking at bright edges on the outer 20% or so, but everything is still crisp and bright.
The XF is just as sharp and detailed in the center of the field, but the image degrades on the outer 20%. Curvature and CA are pretty bad, and you definitely can't achieve nice focus out there. I've read astro reviews on cloudynights.com that suggest the XF8.5 is better about that, but never tried it.
Anyway, bottom line, I'm echoing medinabrit's sentiment. The XF is a very good ep, nothing wrong with it, but the XL/XW series is world-class. I think you'll be disappointed going from the stunning views of your XW14 to the XF. The XF's primary advantage is size and price, but there's no question to me the XW provides a wider, brighter, more comfortable and pleasing view.
I will also say that, personally, I felt after buying both the XL and XF that if you're going to spend the money, spend the money. I tried to cheap out, went half-way and chose the middle-ground (XF), and then when I found a used XL10.5 on eBay for not much more than I paid for the XF12, I realized I should have just gone for it.
Check the classifieds on astromart.com and eBay -- you should be able to find a nice used XW7 for around $260 or an XL7 for $180ish. I think both are a better value than the XF at $160 or so new.
If you'd rather save the money, I'd go with the TMB/BO Planetary eyepiece. Only $99 new, $75ish used, available in several focal lengths from 9mm down, 60-degree FOV like the XF, and just as nice. I don't think the ergonomics (i.e. the eyecup especially) are as nice as the XF, but Pentax is pretty great about that on all their ep's.
