dual ED eyepieces

[Derivious]

Hi everyone,
has anyone had any experience with these eye pieces?
I have someone offering them at a decent price 4140 for 3. i cant confirm any branding when i search them though, just says duel ed. i see a few ebay and online places selling them too.
Any input would be very appreciated

[refractordude]

Hello There


I have the 18mm, 15mm, and 12mm. There was a test study that found that the 15mm was the best of the bunch. That is according to a reply I read at stargazerslounge.com. I would have to agree with that test study. The 15mm is my favorite. All three are way better than stock eyepieces that come with a new scope. I have read that below 12mm the eye relief is kinda tight. In fact the 15mm has better eye relief than the 12mm. The 25mm is a dud. Opinions vary. Here is a link https://stargazerslounge.com/topic/307334-the-bst-starguiders-supertest/


My three main scopes are all F8. Focal ratio is a major factor in eyepiece performance.

[mental4astro]

As with ALL eyepieces, performance depends on the scope design & the f/ratio.

An f/5 refractor is not the same beast as an f/5 Newtonian and as a result eyepieces will perform differently in each. So to say a particular eyepiece is "rubbish" or to dismiss an entire line based solely on the use of a single focal length from a particular line having used said eyepiece in just one scope design & focal ratio only shows the ignorance of the person offering the review. For even an f/5 refractor is different from an f/8 frac, not to mention achromatic vs apochromatic.

Eyepieces are also first designed to work with a convex focal plane (produced by refractors, SCTs & Maks) or concave (Newtonians). Designing & manufacturing for a convex focal plane is easier & cheaper than for a concave plane. Most lines are designed for a convex focal plane but because most people think "this is an eyepiece, this is a scope, it will work" and because of the fear of having their products being branded as 'defective', manufacturers & Brands just won't state this basic aspect of their eyepieces. So people end up buying a particular eyepiece only to become disappointed with the image it produces but this only because they used the eyepiece in a scope not well suited to the scope they used it in.

Take the 150 year old orthoscopic & plossl designs. Orthos were designed for refractors when fracs were all long focal ratios, and plossls for Newts when also long focal ratios. In today's faster scopes, these eyepieces struggle to produce a good image. Not a defect in the design but not being used in the right scope they were designed for.

Add to this that contemporary eyepiece designs are NOT for a single strict design like the plossl or ortho are, but are so named because they produce the same set of AFOV &/or eye relief. Internally they may totally different. A clue comes from the variation in elements often mentioned in the blurb that comes with eyepieces. And the performance of contemporary eyepieces is still dictated by that initial scope design they were designed for.

And designing an eyepiece line that performs really well in all scope designs is very difficult & expensive, and even then there will still be performance differences, including with things such as eye strain (one aspect that is NEVER mentioned).

HOWEVER, there is a hidden bonus to this aspect of contemporary eyepiece design. Because of their non-linear design between focal lengths, while a given line may be designed for a convex plane, there often will be one, two or more individual focal lengths in that line that will perform brilliantly in a Newt! So you will be able to cherry pick an individual focal length from a line that while not designed expressly for your scope, that focal length will do a kick-butt job without breaking the piggy bank!

I do not have experience with those "dual ed" eyepieces - I don't offer advice on eyepieces I don't have experience with. But my suspicions would be that they are designed for optimal performance with a convex focal plane. So when you read up on these eyepieces, make a point of seeing what scope the reviewer has used an eyepiece in & if the image was good or poor - nothing more as most people just don't understand this basic aspect of optics.

You also don't mention what scope you have so it is impossible to give you a straight up reply if these eyepieces suit your scope or not.

"Convex", "concave" focal planes??? Don't scopes focus to a point??? Yes, but only for a single star. And there are stars scattered across an entire field, not all to a single point, so a scope produces a focal plane, not a point and why cameras hae a focus area, not a point. Then, when the shape of this plane is examined it is curved, not flat and will be either convex or concave - why there are "field flatteners" & coma correctors for scopes. How deep the curve of this bowl is will first depend on the focal ratio - the faster the f/ratio the deeper the bowl will be and the more challenging it is for eyepiece designers. 50 years ago there weren't any f/4, f3.3 Newts as an example, and most refractors were f/10 & slower. So while a lot has changed with scopes, the principles dictating eyepiece design hasn't.

To finish, there is NO such thing as "clone" eyepieces. The world of eyepiece design & manufacturing is VERY SMALL. As an example, the Baader Hyperion line is also offered as the Saxon Superwide & the Celestron Duo plus some others. No clones, all the same eyepieces coming from the exact same manufacturer, not some nutter scammer knocking off the original design! :lol: Just a silly urban myth created by people with zero knowledge of how manufacture of optics works or of business. I can go to any eyepiece manufacturer & select from any of they eyepiece designs they have available and select either a generic housing or spend more money on a more customised housing design, and I can call it whatever I want. Clone? Nope. Same eyepiece coming from the same manufacturer but made under a contract. Some eyepiece designs though are made under licence, so these particular lines may not be available to me or anyone else.

If you look in my eyepiece case, most have been selected by me for there performance mostly in one scope design or another. I have few eyepieces I would use in all my scopes - I have Newts, fracs & Maks that go from f/4 to f/13.5. I give each eyepiece a good workout in all my different scopes & see where it performs best, including for eyestrain, and only then do I decide if I keep it or not, most times like I said only to be used in one scope design. I have $10 eyepieces beside $1000 & I use them all without bias on cost or Brand. Best eyepiece for the job.