[Profiler (Profiler)]

Hi Morton

With respect to the specific question of how would the 17mm Delos fair especially if considered in comparison to the Pentax XWs one, albeit simplistic answer, would be that the Delos is much better simply because there is no equal fl in the Pentax range (there is no 24/25XW either which is another gap I suspect many would have liked to be filled). I imagine the closest you could feasibly achieve would be either to use the XW40mm with some sort of 2.5 barlow or the XW30mm with some sort of 1.8 barlow. This is, IMHO, one of the significant real flaws to the XW range which John has mentioned on numerous previous occasions that there are in fact significant "gaps" in the focal lengths of the EPs. This is why many folks who have the XWs also tend to have the 17mmT4 nagler as well to plug the gap in the XW range. The 17T4 IMHO is an excellent EP however - ironically - I have also thought of possibly buying the 17mm Delos as a possible replacement for the 17T4 which is roughly 750grams and 2'. Whereas the Delos is about half the weight (i.e. akin to a XW if such a thing as a 17mm XW existed) and is 1.25 and thus a match with all the other XWs (20mm and down) in terms of filters etc.

I tend to agree with John that the great "curvature" problem in the higher Fl XW's is grossly overstated. I have spent considerable time looking through the 14 and 20 and in my scopes (all refractors) I really can't perceive anything. Ironically, the one EP which I do seem to perceive something is my 17T4 however it really seems neglible "to me" and certainly not something worth discarding the EP over. It is good to make people aware of this possible issue with the long focal length XWs but I also agree from my own experiences that it is something which, as John has previously mentioned, perhaps only arises in some scopes with some people.

Finally, I would have to say that a lot of this discussion is academic and abstract as, akin to Johns previous comments, Televue and Pentax both make superb eyepieces and it is a toss of the coin but ultimately a win, win situation with both as I can't see how people would be seriously disappointed with purchasing either as they are both extremely good. My own feeling is that the attributes which mostly differentiate many of these EPs are more to do with things like ergonomics than anything else. Consequently, it really boils down to what you specifically require from the EP rather than whether one is, in simplistic terms, purely better than the other.

Many years ago I was told A astronomy was all about 'compromises' in terms of getting one feature or attribute at the expense of another. In hindsight I realise that this was a very valid insight into the equipment for this hobby.