Quote:
Originally Posted by manny
So what criteria comes into play when we buy eye pieces?. ... .So do we really have to spend big bucks for little improvement? what do you think?
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Manny,
Hello. This question is always an interesting one because I think the answer lies not where one expects. When talking an eyepiece I think most will think the list of criteria should be relative to the optical performance of the eyepiece. I think this is not the case. Sure it is a consideration, but by far not the entire story.
For me, I find what makes a great eyepiece is when all of its different attributes come togather in such a way that it meets or exceeds my personal expectations. For me, I generally look for a FOV that is sharp over 85%, so I'm not too concerned about that outer portion near the field stop since I am not a field stop observer
Build quality and ergonomcs then come into play...I do not like overly large eyeieces and I like them to feel good when being handled. I am less concerned about eye relif and more concerned about eye positioning behavior...so how well is the exit pupil designed for my preferences. I don't like them to be too sensitive to eye placement...and further, the designer has a choice of where they form the image with the exit pupil...they can place the image formation near the cornea of the eye...or have it form in the center of the eye. In the case of the latter, you can then glance at the field stop in wide fields without the FOV going partially black. The XWs are like this...you can roll your eye around and the entire FOV stays brightly lit. Many other wide fields are not like this.
So it's lots of little things that define my personal preferences and optical quality is not the only one or the primary one. Case in point is I owned both a 12T4 Nagler and a 13mm Hyperion and kept them both for about half a year deciding which was best for me. The 12T4 put up a little better view, especially being sharper near the field stop (it was not sharp at the field stop), but to see the entire FOV I had to dip my eye very close to the eye lens. The Hyperion was more comfortable to view, and the FOV was almost as sharp in the off-axis as the 12T4, plus ergonomically its dual skirt design was much easier to use than the 12T4. In the end, I sold the 12T4 and kept the Hyperion.
So to make the determination of whether it is worth it to upgrade to another brand or line, I think it has less to do with the optical performance and more to do with is there some set of features in the new eyepiece that are accomplished much better in the new eyepiece. if so, then an upgrade is probably somethign that will satisfy you. For me now, I have the Pentax XWs as my wide fields. Some others out there have better off-axises, but none I have viewed through have better on-axises. The XWs have a superb on-axis being low in scatter and sharp and tone neutral and this all makes star fields for me to pop with a 3D-like view. While there are other eyepieces out there with more expansive AFOVs and maybe a better far off-axis in the longer focal lengths...this is not a big enough deal to spend more money. Now if someone could put the XW performance in the package of a Plossl, then that would turn my hear...and eye I'm sure
So in the end, I feel eyepieces are like gloves...you just gotta try them to see which fit you personally the best...and then they become the best, whether that is a Plossl or some uber wide field. And as long as you are not disatisfied with your eyepieces, then there is zero reason to replace them, even if they are Huygens!
-Bill