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Fox,
Just something else to ponder. As Scott Mitchell just mentioned we used my 14mm Pentax XW in my 18"/F4.5, 3RF Obsession telescope last Saturday night. Even in the fast F4.5 newtonian it performed wonderfully well, a little bit of field curvature towards the EOF but superb on axis and across at least 85% of the FOV. As a comparison, we viewed NGC253 in the 18"/F4.5 Obsession with both the 14mm Pentax XW and Andrew's (Rocket Boy) 17mm Nagler T4. The Pentax was better than the Nagler in just about all respects, including it's correction at the EOF.
However, I am firmly of the view that a paracorr would "clean up" the view considerably in the 17mm Nagler T4 and may not necessarily offer an enormous improvement in the 14mm Pentax XW.
I am sure you will really enjoy the 14mm Pentax XW in that 4" APO.
CS-John B
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