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Eyepiece elements and groups


bomberbaz
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Most manufacturers now give out the design schematics for their eyepieces. eg Pentax 10mm XW 8 elements / 5 groups  or Nagler 6 11mm 7 elements / 4 groups.

Is there any general link between number lens and groups that gives an indication of quality of what you are possibly getting?

I am getting a 4" frac (F6.6/673 FL)  and one of the reasons is to get great big panoramic views and so looking at something around 30/33mm / 70+ fov. (there is no way i am putting my Nirvana into a diagonal)

Anyway,I came accross this http://www.opticstar.com/Run/Astronomy/Astro-Accessories-Telescopes-Ascension.asp?p=0_10_5_1_1_0 which is where I am thinking of getting the scope from and just wondered how it might perform and that is when the question popped into my head, is there any correlation between elements & groups!

Any thoughts?

Steve

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I don't think there is a link Steve. What matters is the quality of the execution of the optical design, the accuracy of the lens figuring and polishing, the glass types used, the quality of the light baffling in the eyepiece, how the lenses are mounted, the quality of the coatings applied and a number of other things. You can take a decent optical design and mess it up by just getting a small factor wrong. Doing it well usually leads to a higher price ticket.

The eyepieces you link to have been around for years under different brandings including Moonfish who marketed them rather well a few years back. They work well in slow scopes (eg: F/10) but you get what you pay for generally, in terms of performance, when you use wide or ultra wide eyepieces in fast scopes. Your Nirvana will out perform them by a long, long way and would be superb in the 102mm F/6.6 refractor. I use my Nagler 31mm in my Vixen refractor which is very similar spec and it's really good :grin:

Get a compression ring diagonal and enjoy the astigmatism free ultra wide views that the 28mm Nirvana gives :smiley:

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I thought there might be some how with the bettere ones lookking to have mkore groups usually !!

I am going to try and prove you wrong John, don't know how but I will  :grin:

Steve,

I'm only giving you my experience with eyepieces and scopes that I've used over the years. I've not used everthing on the market by a long way nor have I read and so go for it and good luck to you !  :smiley:

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ermm,would you care to explain what is wrong with Nirvana? yes Nirvana is not equaling TV or Pentax,but damn,there is absolutely nothing wrong with that eye piece.it is not a televue by all means,but still it is a great performing eye piece and MILES better then that over copied eye piece you linked.To get good performance on 30+mm Ep`s ,glass elements have to "grow" too,Nirvana is big,TV T5 31mm is a "holy hand granade".if you really want a good corrected 30mm wide field eye piece,you will have to look at good brands in likes of televue,pentax XW,only alternatives which will be close to performance of the first 2 would be meade 5000 series 30mm UWA and ExSc 30mm 82 deg.They will be close to TV performance,possibly will match on something,but will not do anything better then TV does.

But as you already have Nirvana,will it be financially beneficial to sell your Nirvana just to get Meade or ES if you cant afford TV or Pentax? Hell NO!

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Hi Steve, I have no experience of the Ascension UWA but do have a 38mm SWA. In my C11 the view is excellent in the centre but stars become noticeably elongated towards the edge. I would expect the UWA to be slightly worse???? I will leave it to others with more experience to suggest alternatives.

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I thought there might be some how with the bettere ones lookking to have mkore groups usually !!

I am going to try and prove you wrong John, don't know how but I will  :grin:

John I was only kidding, I was trying to hypothesize but I know your right really

ermm,would you care to explain what is wrong with Nirvana? yes Nirvana is not equaling TV or Pentax,but damn,there is absolutely nothing wrong with that eye piece.it is not a televue by all means,but still it is a great performing eye piece and MILES better then that over copied eye piece you linked.To get good performance on 30+mm Ep`s ,glass elements have to "grow" too,Nirvana is big,TV T5 31mm is a "holy hand granade".if you really want a good corrected 30mm wide field eye piece,you will have to look at good brands in likes of televue,pentax XW,only alternatives which will be close to performance of the first 2 would be meade 5000 series 30mm UWA and ExSc 30mm 82 deg.They will be close to TV performance,possibly will match on something,but will not do anything better then TV does.

But as you already have Nirvana,will it be financially beneficial to sell your Nirvana just to get Meade or ES if you cant afford TV or Pentax? Hell NO!

Dude, aint nothing wrong with the Nirvana, I love it. Just I wasnt thinking of hanging it out of the back of the frac however i may now reconsider buying new ep's to fit the scope and instead buy a quality diagonal instead, it would actually make more sense come to think about it.

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Steve,

I would go with what Dude with the Tube mentioned the 30mm UWA Meade, an almost forgotten eyepiece that I had. There is a review somewhere on Cloudy Nights where purely on price the gentleman went fot the Meade over the Nagler. I had the two together but never reviewed tham as such. In my scope it was only that last few percent of FOV that was ever in question. I will say this though, while not as sharp there it also was not as distorted. The times I use the Nagler 31mm to view the Moon are very rare but in my opinion it looks awful though this eyepiece and I sold my 26mm Nagler just for this reason as I did use it on my LX with it's 3 meters of F/L.

As big a fan as I am of TeleVue, I also like what I see to look about right as well.

Alan 

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i think you are referring to this post Allan:http://www.cloudynights.com/page/articles/cat/user-reviews/eyepieces/meade-eyepieces/meade-5000-30mm-uwa-r1223

Having had both Meade and having now ExSc 30mm, i would say that despite Meade was a very good eye piece,i think ExSc presents the view better.ExSc is a bit more sharper to my eye,better corrected and doesnt suffer with on edge performance what Meade had.Again, i cant really say Meade suffered with it.It is a bit too strong term and differences between ExSc and Meade are very very tiny and i am really talking about difference what will be seen only on great night what doesnt happen very often.Both these big granades are well worth and whatever you go for,they will give you very pleasing reviews.

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Why are we talking about the Meade / ES 30mm 82's when the OP already has an excellent 28mm 82 Nirvana ?.

I believe the intention of the original post was to explore whether a lower cost ultra wide would compete with the higher priced ones, assuming that a similar optical design was employed. Steve was just not keen to stick the big expensive Nirvana in the 102mm F/6.6 refractor but my view is that it will do a great job.

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hahaha, no applogies needed Alan seriously, although I did wonder where the thread was going.

As John said I was considering looking at some cheaper EP's to use with the new frac that is due to arrive and was hypothesising over possibly expending my ep collection to use with it. However having been corrected in my rather unilateral thinking I wil instead buy a decent diagonal that clamps up really tight and use my current collection of glass.

Edited by bomberbaz
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