Another point I want to throw upon the table is the observer's awareness of their own color sensitivity. In my mind, this is similar to the observer's awareness of their own interpupillary distance, eye pupil size (dark adapted and daytime), facial bone structure, or binocular weight and size they can comfortably hold in their hands.

The point on the table--now hear this--I think observers should develop an awareness of their personal sensitivity to colors. This probably will not come with the purchase of the first optical instrument. And this awareness may not come until they own several instruments and have done a considerable amount of optical observing.

The awareness of our unique color sensitivity, along with our personal field comparisons of several ED/nonED models, may influence whether we decide to add one or more ED binocular models to our selection of optical instruments.

I did this with two separate models--Swift Audubon 820 ED 8.5x44 porro and Pentax DCF ED 10x50 roof--and I decided to invest additional money and go for the ED versions. Now, two years later, I am glad that I did.

Others may see it differently.

. . .

A related issue to the observer's awareness of color sensitivity is the observer's color preference.

Myself, I find that I enjoy a Minox color rendering in the fall and winter seasons, and the Pentax color rendering in the spring and early summer. Of course, what I am seeing is really a type of chromatic aberration--albeit, in my eye, a very pleasant chromatic aberration.

Others report they prefer neutral color or no color bias in their binoculars. I must confess that most of the time I prefer neutral color when I view. This is one reason I frequently observe the night sky with Nikon SE binoculars. Of the binoculars in my selection, the SE is most neutral. Someday, I would like to compare the SE color rendering with the Leica color rendering, which is advertised as the most neutral glass around.

As for my selection of telescope eyepieces, I have decided to build a complete set of the Pentax XWs, which some observers report to be more neutral than the Televue assortment. With telescope observing, I am learning the eyepiece quality is an important component to the observing experience.

. . .

How about ED glass for night sky observing?

Much has been written in this thread about daytime observing with ED binoculars. I confess I have contributed to this more than most by posting links of similar discussions from the Bird Forum.

However, I find ED binoculars have their niche in night sky observing with 8x or 10x ED binoculars:

Sure, my 12x50, 16x70, or 22x85 will see more stars and DSOs than either my 8.5x44 or 10x50 EDs.

But when I desire to relax and enjoy the color of the night sky, I cover my Dob and large binoculars, head for the chaise lounge, and let the ED binos fill me up with color. I particularly like the way the orange and red stars pop in the Pentax DCF ED binocular. I also enjoy the color of the night sky with a 70mm ED refractor and a Pentax XW 40mm wide-field eyepiece (11x, 6.6 exit pupil, and 6.5° FOV).

But I have found that when I pass the ED optics to family and friends, they do not rave about the color as I do.

I wonder if they see what I see?

I am finding this to be a difficult question to discuss. I have tried to leave the optical engineering to others who know much more than I ever want to learn. Particularly our forum moderator EdZ, who is fantastic. And Brock, who never ceases to amaze me with bi-lingual postings.