Quote:
Originally Posted by mr bruess
I also have a superview 20mm. it is very good budget eyepiece.it is sharp to edge in my 90mm meade star navigator but not with my 10 inch dob
|
Mr Bruess note here is a VERY important one here. AND clues are being given by others as to the BEST SCOPE for the SuperView eyepieces.
What am I getting at?
Eyepieces are actually designed to be matched to a particular scope design, be it a Newtonian, refractor, SCT, Mak, etc. This is because the focal 'plane' produced by a scope is actually not a flat one, it is curved - Newtonians produce a concave focal plane; refractors, binos (binos are not simple refractors either) SCT's and Maks produce a convex focal plane. Eyepieces in turn, because they are designed to work with a particular native curved focal plane, they will work brilliantly with one shape and poorly (if not crap!) with the opposite shaped curve.
Remember, this does not mean that there is a fault with the eyepiece. There isn't. Telescope optical geometry is much more complex than we think of at first. It is only when we start trying to take photos that we begin to experience an unevenly focused field in our pictures, or a highly distorted image in our eyepieces do we begin to get our first notions of things not being so simple. Then we begin to resort field flatteners, field correctors, coma correctors (not an immediately related aberration, but ultimately it is a related cousin) to help eliminated these problems.
Add into the mix a staggeringly large variation in f/ratio within any one scope design (Newtonians go from f/3.3 to f/20, refractors f/5 to f/30, etc), and even the radius of the focal length, and then we begin to really get a sense of the complexity in eyepiece/scope matching. And I haven't even added the order of difficulty that different eyepiece designs, focal lengths, coatings, glass types, etc, all add to the mix!!!
All is not lost though,
While there are eyepieces that are good only in one scope design and poor in others, there are some that can do very well in one and ok in others, and a few that can do very well in just about all! Some of these are surprisingly inexpensive, like the SuperViews (great in refractors and ok in Newt's). Some are much more expensive (Vixen LVW and TelVue Delos lines). But with ALL of these, there will be variations in performance within their different focal lengths - there has to be, and this is both visible and noticeable with eye strain. Only adding to the complexity here, within the one eyepiece line that is designed for a particular scope, there can be just the single focal length piece that actually does do well in all scope designs!!!
BIG bucks is not guarantee of similar performance of any one eyepiece line doing well in all scopes either. The excellent Pentax XW line is one of the more obvious ones. These are excellent eyepieces, BUT some focal lengths are definitely only for one scope design and not for others.
The biggest problem we have a consumers is the manufacturers do not tell us these things. They fear having their equipment being misinterpreted as 'faulty'. Truth is the complexity of the eyepiece/scope equation is so big, and most people do not have the understanding nor the inclination to want to understand, that the manufacturers find it safer to not say anything. Then we few who are actually interested in optics, get it in the neck with misinformation and spending big $$$ on gear that does not work (match is the better phrase), and we do not understand why,
Yes, I like the SuperView line. These are a take on the old Erfle eyepiece design. In a refractor these are very good, good in SCT (these have reflecting components that add their own set of aberrations), and good to ok in Newt's (depending on EP focal length). Just understand that their price is not a true or remotely complete reason for their variation in performance. There's a little more to this...
Mental.
+1 for the 15mm super view .
