Dave,
This was something I alluded to recently in this post on the 14mm Pentax XW
http://www.iceinspace.com.au/forum/s...ead.php?t=8815
Quote:
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Originally Posted by ausastronomer
FWIW, the 10mm Pentax XW is a slightly better performer than the 14mm Pentax XW IMO, particularly in fast newtonians *** and is one of the best eyepieces I have ever used in any telescope. You can stack whatever Nagler you like up against it. In addition the 7mm Pentax XW is just as good as the 10mm.
*** The 14mm Pentax XW when used in a fast F-Ratio scope having a curved focal plane such as a Newtonian, exhibits mild field curvature. Its minor and not an issue IMO. This is not evident to any degree with the 7mm and 10mm Pentax XW's. The 14mm Pentax when used in a telescope design having a flatter focal plane such as an apochromatic refractor does not exhibit this field curvature.
ENJOY !!!!!! sounds like you're already converted 
CS-John B |
I saw your thread the other day, but haven't had time to reply in the required detail, it gets quite complicated and necessitates a lengthy reply to explain it all properly. I may not have the chance to do this for another couple of days but will do so when I have more time. In the interim, this book contains a lot of the answers if you have access to it at your local library or Astronomy Club Library. Its actually a book worth owning IMO, if you're interested in what makes all this stuff tick
https://www.willbell.com/tm/tm6.htm
CS-John B