Based on my experience, Don is 100% correct- every Nagler I've used has been "soft" near the center of the field. Even my mid-priced orthos do better than Naglers as far as definition goes. This isn't noticed at low powers; at high powers typically used for plantary observation and close double-stars, wide-field isn't needed. The Ealing can sometimes have troublesome tube currents for the first few hours of observation. It takes that big primary a while to cool down. But this is usually easily identified as separate from diffraction limitations. On 4/27/07, Don J. Colton <djcolton@piol.com> wrote:
Unfortunately the Naglers do not do that well at high power because of the number of elements. I have found that good plossls, the Takahashi and the monocentric are the best performers.