Eyepiece Design

[Charic]

We have Naglers, Plössls, kellners, Abbe, Erfle, Branden  and Ramsden, all respected in one way or another, by the  folk that use them, so is it fair to say that  Astro Tech, and the many branded clones ( BST Starguiders? ) all using the same six lens, 60° optical design, that is, the Paradigm Dual ED,  could simply be called a Paradigm to give them a place in the grand scheme of things ocular.
 

[John]

The nearest "classic" design that I can find to the Paradigm / BST Explorer / Starguider etc is the Pretoria. They are not quite the same though and I've no idea if the Pertoria design was ever executed using some ED glass elements. Trouble is, on this forum the term BST Starguider / Explorer is known wheras Paradigm (the Astro Tech branding of the eyepiece) is not. Maybe the same or a very similar design is used in other eyepiece ranges as well, such as the Celestron X-Cell LX ?:

[mikeDnight]

Hi Charic,

I suppose for simplicity you could refere to branded clones under the same title, but unfortunately it would be no indication of optical quality. There are many eyepieces branded "Abbe" for example and yet they vary greatly in quality. For that matter even the revered Nagler eyepieces vary greatly in performance, and boasting a wide apparent field is no guarantee of edge of field quality, neither does the term "Abbe" tell you much. Recently I bought a double set of well known HD Abbe orthoscopics for use in my binoviewer, yet although they were well spoken of by many, the set i had were unbelievably poor performers and had to be returned. Also, some cheaper end Plossl or Kellner eyepieces, though cheap and cheerful, can be stunning performers and buying expensive branded models of the same design may show no better performance, and sometimes worse.

Mike

[Ruud]

Hi Charic,

Chris Lord of the Brayebrook Observatory compiled an eyepiece chart that traces the evolution of all kinds of designs:

           Lord-Eyepiece-Evolution-Tree.PDF

At the bottom left of the chart are the negative-positive designs. The Fleischmann, dating back to 1977 is the oldest mentioned there.

The Klee-Pretoria, from 1985, is there too, in the compensating group. This eyepiece, if I remember well, is a coma-correcting design for newtonians. The Pretoria is not suitable for coma-free telescopes, as it would introduce 'anti-coma' and ruin the off-axis image that way.

The compensating designs are on a small branch of the eyepiece tree. Most eyepieces on the chart are general purpose. All aim to improve over earlier design and to get as close to an ideal image at as little cost as possible. There is still plenty of room for improvement, so I suppose there will be a many more designs to come. 

Unfortunately the details of new designs are often kept secret, to prevent imitations from being made. It is said that Televue no longer applies for patents to protect their designs from being copied by competitors.

[Charic]

2 hours ago, John said:

The nearest "classic" design that I can find to the Paradigm / BST Explorer / Starguider etc is the Pretoria. They are not quite the same though......

Cheers John,  hence my reasoning to have them described as  a particular design.
I`ll still call them Starguiders for now.

 

2 hours ago, mikeDnight said:

...........some cheaper end Plossl ...... though cheap and cheerful, can be stunning performers.......
..........buying expensive branded models of the same design may show no better performance, and sometimes worse.

With you there , I favour my Revelations over the other Plössl's in my collection, and as for expensive  EP's,  although TeleVue Delois are in a different league to my Starguider's ,  there's no real difference overall in the image I see,  apart from the wider field from  the Delos design, but  overall, if the image from a Delos is better, then it's very subtle,  to my eye.

 

1 hour ago, Ruud said:

Unfortunately the details of new designs are often kept secret, to prevent imitations from being made. It is said that Televue no longer applies for patents to protect their designs from being copied by competitors.

As is often the case. 

[Don Pensack]

The manufacturer just calls them 1.25" ED eyepieces (hardly a unique qualifier) and there are at least a half dozen resellers.

http://www.barsta.com/show_hdr.php?xname=MDA8V11&dname=OPFOR71&xpos=13

To clarify the source, one could just use the mfr's name, such as "the ZZZ ED 60° eyepiece, sourced from Barsta".

The only caveat I can think of in doing so is to state they are, in fact, identical.  That may be true, in this case, but you don't know so because

coatings might vary, or internal baffling, etc., based on what the reseller ordered.  Slight differences might account for price differences but might not even be mentioned in the brochure/web info from the reseller. 

Difficult info to obtain, often, unless you know someone working at the factory.

 

[Charic]

Cheers Don.

Even my friendly vendor spoke and  suggested I look at the Paradigms, and Barsta ( that word is so close! hate it, although I can see where BarSTa  was derived from? ) as the the only source of information  from the internet, regarding these EP's.
As I mentioned to John, I'll still refer to them as Starguiders, for now!

[John]

If we clubbed together and ordered enough of them from Barsta we could call them whatever we like !

It's interesting to look at some of Barsta's other eyepiece products, some of which are rather familliar:

UWAN / Nirvana's: http://www.barsta.com/show_hdr.php?xname=MDA8V11&dname=OPFOR71&xpos=8

Telescope Services Expanse: http://www.barsta.com/show_hdr.php?xname=MDA8V11&dname=OPFOR71&xpos=10

Low cost 80 degree EP's (solds under loads of brand names): http://www.barsta.com/show_hdr.php?xname=MDA8V11&dname=OPFOR71&xpos=9

Skywatcher UWA's: http://www.barsta.com/show_hdr.php?xname=MDA8V11&dname=OPFOR71&xpos=11

I think Don poses a question which has been discussed on here a few times - are all the different branded versions of these eyepieces exactly the same or are there variations to the specifications specified by particular brands ?

I tend to agree with Don's conclustion that we will probably never know for sure unless we get some inside information.

At least, if you use the term BST Starguider, most on this forum will know what you are referring to

 

 

[Dave In Vermont]

I find the chart below is useful for quick reference on many eyepiece designs. I keep a copy on my wall.

Have fun,

Dave

 

 

 

[Ruud]

It's a mystery. 

The UWANs / Nirvanas are not just made by Barsta (see the link by John above)  but also by Kunming United Optics: http://www.united-optics.com/Products/Telescope_Accessories/Eyepieces/UWA_Eyepieces/UWA_Eyepieces.html

And these United Optics SWAs 70° look just like the Barsta 70° at the bottom of this link by John.

I have a 16mm Nirvana. It's a nice eyepice.

 

[Dave In Vermont]

Just to add more confusion - try these SWA's:

http://www.universityoptics.com/2inch.html#WS70

These seem to be 'branded' all over the map. And here they are yet again:

http://www.telescope.com/Accessories/Telescope-Eyepieces/Orion-Q70-Super-Wide-Field-2-Telescope-Eyepieces/pc/-1/c/3/sc/47/e/66.uts

I can find several others as well. I have these from my first link. I think they do a very nice job.

Have fun -

Dave

[John]

6 hours ago, Ruud said:

It's a mystery. 

The UWANs / Nirvanas are not just made by Barsta (see the link by John above)  but also by Kunming United Optics: http://www.united-optics.com/Products/Telescope_Accessories/Eyepieces/UWA_Eyepieces/UWA_Eyepieces.html

And these United Optics SWAs 70° look just like the Barsta 70° at the bottom of this link by John.

I have a 16mm Nirvana. It's a nice eyepice.

 

I've thought for a long time that the far east manufacturers either share or sell designs for these things between themselves. I wondered that about Japen when the Baader Genuine Orthos went out of production supposedly due to the earthquake/tsunami only to be replaced by very, very similar designs just a few months later under other brand names.

The chinese based factories may be under some influence from the chinese government to share products that are popular in the west to ensure the maximum revenues coming into the country ?

Edit: I'm going to commission a Wild-Scidmore-Dillworth hybrid design just for kicks - anyone want one ?

PS: It's going to weigh around 6kg !

 

[Charic]

12 hours ago, John said:

If we clubbed together and ordered enough of them from Barsta we could call them whatever we like !

This is true, I've  even thought about it  myself.  

Lets jump back a little,  its not the brand name that I'm  proposing, its the design pattern.

Take a Plössl. Whoever actually constructs these eyepieces  for TeleVue, Revelation, Meade and others, the eyepiece is constructed as a symmetrical composed of two doublet lenses, and even with subtle  variations  here and there,  the eyepiece itself is still a Plössl.

The fact that I have not seen any diagrams to resemble any likeness to  any of the nine or so  ED variants in circulation, except for the paradigm image, is why I posed the thread, and searching alone for ED eyepieces  returns  eyepieces that are not similar in shape or form? 

When I mention BST Starguider it just describes the brand, not the  type of eyepiece, yet when folk say use or try a Plössl, I/we know exactly what they mean.
If I named all nine brands (that I'm aware of) regards the 1.25 ED's I`ll  only get asked, "which one is the best!" .....the Starguider would be my reply, simply as it's known to me as being the cheapest, available, here in UK when bought new, but the rest will probably provide the same image result under the right conditions, given the same scope. But If I said  their all  Paradigm derived! That surely would be simpler, the user than chooses a brand?  simple!

Another example, take the TeleVue Delos! What type of eyepiece is it... it would appear to just have a brand name, rather than a  design specified title?  I just know it as a Delos!  named partly after its inventor who may have been on holiday on  a small Greek island at the time?
Its true that the Delos was conceived from the Ethos project,  providing the same if not similar image quality to the Ethos, but  with less field of view, but also ( from browsing)  the Delos  was created to better  the Plössl design ( design or not, the Delos is not a Plössl)  by giving the user more eye-relief ( especially for spectacle wearers ) and a greater field of view.  I thought you can only change or better something of the same design by changing the design, and owning the patent, which TeleVue have done in the past

I'll refer to my EPs as Starguider, save any confusion 

This thread is becoming more of a ramble, than I  had imagined, so maybe it can get Modded into the lounge?

[triton1]

But then to confuse things more most people on here not so long ago used to refer to them as "explorers".

[Charic]

JONN.........They still do , on one site there's  a  BST Explorer-Starguider ED15   and  they also have the 25mm BST Explorer ED  Paradigm ,  with 'Paradigm'  stenciled to the  EP body, with  yet another brand name, so that's TEN re-sellers  on the go!

Its even their "Rolls Royce version" as stated in the description, surely now, that's a  good enough  reason to buy one  

Like you say, all very confusing?
I have nothing against this company, they have served me well, maybe it's  just their own moniker. 

Explorer before Starguider , but  copyright rules  & regulations dictate,  therefore Starguider was born.

[John]

Perhaps we should just call them "Charics Favourities"