Quote:
Originally Posted by cydonia
Hi John and Starkler,
Thanks for your replys. I'm going to go for the 30mm XW, Yes it cost more than the 27mm Pan, but it is water proof so it will keep moisture out. I've heard that this can be a problem in non water proof eyepieces.
The troubles outlined in another thread here about the 20mm XW are not present in this focal length?
Cheers
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Nope, the Pentax XW series are not a "scaled" design. Hence the lens configuration and element design is different from one focal length eyepiece to the next. Consequently they are not all identical in their performance characteristics.
The best of the XW series are the 5mm, 7mm and 10mm in 1.25" barrel and the 30mm in 2" barrel. These all exhibit a flat field in just about any telescope. Despite what you may read from many, the other focal lengths are all exceptionally good eyepieces. Whilst they may exhibit some field curvature in some telescopes, they outdo all the "widefield" competition in terms of comfort, sharpness, contrast and light throughput. Further, if your scope is a fast newtonian the field curvature issues are fixed by using a paracorr.
Cheers,
John B