[Wavytone]

Don I disagree. You imply most eyepieces - even the cheap ones are reasonably good. This is simply not true - there are bloody awful ones out there which belong firmly in the trash. While it is true that something as deceptively simple as a plossl works well in a Newtonian, or a Ramsden or Huygens in a refractor - these are invariably a good match for the scope they are used with. And a little optical analysis will show why.

Your asertion assumes all telescopes are more or less equally good - and give flat fields free of the monochromatic aberrations. That simply isn't the case - compare the field curvature of newtonians to that of refractors, as well as SCT and maks.

It's already obvious that each type of eyepiece will suit some scopes, but not others, due to field curvature alone. Certainly not all. Several members in this forum have done side by side comparisons to establish this. To the extent a fair amount of buying and selling has occurred as observers try to optimise their eyepieces to match their scopes, once they know what works well - and what doesn't.

Anyone who made the mistake of buying Koenig eyepieces will understand this, most ended up fairly rapidly in the trash IMHO.

There are other issues with specific eyepieces, too. Some Naglers are notorious for "kidneybean", due to excessive amounts of spherical aberration in the eyepiece.

It's also evident that the designs of virtually all premium eyepieces since 2000 contain some amount of field curvature and negative coma, to suit fast newtonians while remaining tolerable in SCT's and maks.

IMHO it's high time eyepiece manufacturers started to state which type of scope their eyepieces are optimised for, instead of keeping this a dirty secrecy and leaving observers the task of finding out by trial and error.

If this happened buyers might actually be able to make rational choices - instead of finding out by trial and error.

I have been tempted to set up an optical bench to test eyepieces and publish the results (I have a physics degree and a long background in ATM and have designed optics before). I'm also quite sure some manufacturers will have a heart attack at the thought of this, and would dearly love to kill that information off.