Hi all,
Having poo-pooed the idea of getting another Ethos for some time now, I finally took the plunge and picked up a 17mm Ethos from Bintel at SPSP last weekend. And I am glad I did!
I remain a big fan of Nagler eyepieces. My workhorse for many years has been the 20mm T5. It provides a good compromise in most conditions in the Mary Rose. With Paracorr, which is how I always observe to remove any coma, the 20T5 provides a magnification of 146x, with an Exit Pupil of 3.5 and a TFOV of 32.4 arc minutes. This provides an excellent context in which to observe most objects other than the very large ones, for which I move to the 31mm "Terminagler". The only downside of the 20T5 is the somewhat tight eye relief of 12mm, which I don't mind but others do especially if they observe with glasses.
So what about the 17E? Well I took the opportunity offered by John Gerkin (Xstream) and Anna Novak (Anna) at SPSP to try their 17E and 21E in the Mary Rose. Both eyepieces were fabulous, but what particularly struck me was that the additional magnification of the 17E brought out a lot more detail in the deep sky targets, with a darker background sky. At the same time, it still yielded a good TFOV, and the magnification was not so high as to render the EP unusable in average conditions. In short, this was EVEN BETTER than the 20T5!
The stats of the 17E in the Mary Rose (all with Paracorr): Magnification 172x , Exit Pupil 3mm, TFOV 34.8 arc minutes. What is noticeable is that the TFOV is larger than the 20T5, whilst ramping up the magnification and contrast a notch. As with all Ethoi, it has an ER of 15mm which is just a little more comfortable for everyone.
The results have been great. Both at SPSP and again last night whilst observing in my backyard on the NSW Central Coast, I enjoyed razor sharp images at the higher power and better contrast of the 17E without any concern that the conditions may not be able to support the magnification. I was able to draw out excellent detail in the Homunculus last night under suburban skies, and it frames numerous OCs and Globs beautifully.
The 17E has become my new workhorse!
Will I get the 21E as well? Probably not. The 17E and the 31T5 are parfocal, such that if I really want a larger FOV of the night sky for the largest objects, the 31T5 will be fine, especially under dark skies where the 31T5 comes into its own without having to fight against lighter skies.
I am a big advocate of keeping things simple. Don't have too many eyepieces. Just have a few fantastic eyepieces, and make the most of them. My advice is to work out the sweet spot for your scope, and get yourself the highest quality wide field eyepiece at that focal length that you can afford.
