ちはる 5 I used both 12,5 and 17mm Nikon HW eyepieces, and could compare them with the Ethos equivalent on a T500 F3,9 Newton telescope (with and without paracorr). The Nikon won the match on their ability to present a near perfect image on all the apparent field, from center to border. The Ethos did great, but a little less than the Nikon. Beside, I liked the fact that the NAV-HW are delivered with their native barlow x1,2 lenses, which gives you two power per eyepiece : the 12,5mm is also a 10mm and the 17mm is also a 14mm. There is no better eyepiece in the 100° apparent field of view family.