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Incredible Value For Money!

Damo636

By Damo636
in Discussions - Eyepieces

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alan potts

alan potts

Posted
Posted

Yes but you will have to put postage and import duty on that but still very good value. The Meade 30mm which is proved to be very close to the Nagler is priced well at Telscope House, 250 I think.

I don't have any Ex Sc ep's may it's time to look at some.

Alan.

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Carbon

Carbon

Posted
Posted

I'm thinking about pulling the trigger on that EP before the sale ends at the end of the month. I was also considering the Meade but it is close to a pound heavier than the ES. I'll definitely end up with balance issues on my dob.

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John

John

Posted
Posted

I much pefer the look of the Baader 31mm Hyperion Aspheric, which is lighter, cheaper and although it has only 72* apparent field, is much more usable.

How it it's edge sharpness at F/5 and faster ?.

I'd read that the Hyperion Asperic's are about the same as the Aero ED's / TMB Paragons in this respect, which are OK but by no means perfect.

They are much lighter than the 30mm UWA's though !

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sologuitarist61

sologuitarist61

Posted
Posted

Does anyone know why they are so darned BIG???? The piece of glass you look through seems quite small, so I cannot imagine the elements inside are that big, are they???

Or is it just a case of 'we are selling you an expensive EP so we have to make it look worth the price?'

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John

John

Posted
Posted

Does anyone know why they are so darned BIG???? The piece of glass you look through seems quite small, so I cannot imagine the elements inside are that big, are they???

Or is it just a case of 'we are selling you an expensive EP so we have to make it look worth the price?'

With the Nagler 31mm there is at least one lens / lens group inside it that is around 80mm in diameter. I've seen a diagram of the light path through the eyepiece and it does use the full width of these lenses. I guess this is how you produce a very wide field of view combined with low / no astigmatism at the edges of the field of view, even with fast scopes. Oh, and you have to try and control field curvature and other aberrations too.

I've used a 30mm 84 degree FoV eyepiece that was not as fat as the Nagler / UWAN / ES 82 and that worked fine at F/10 but was frankly awful at F/6.

These UW eyepieces use expensive ED glass types so I don't think they would use lenses larger than is actually required.

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sologuitarist61

sologuitarist61

Posted
Posted

With the Nagler 31mm there is at least one lens / lens group inside it that is around 80mm in diameter. I've seen a diagram of the light path through the eyepiece and it does use the full width of these lenses. I guess this is how you produce a very wide field of view combined with low / no astigmatism at the edges of the field of view, even with fast scopes. Oh, and you have to try and control field curvature and other aberrations too.

I've used a 30mm 84 degree FoV eyepiece that was not as fat as the Nagler / UWAN / ES 82 and that worked fine at F/10 but was frankly awful at F/6.

These UW eyepieces use expensive ED glass types so I don't think they would use lenses larger than is actually required.

Thanks John for the explanation, it must be an extraordinary light path through the EP I would imagine. I am fairly clued up on photo lenses but I guess EP's have a different set of rules.

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John

John

Posted
Posted

Here is the Nagler glass layout showing the light path through the eyepiece - the eye would be placed to the right of this diagram. Each lens has to be precisely figured and polished and a number use exotic (and expensive) ED type glass. The air-glass surfaces have multi-coatings applied and the lens groups have to be mounted precisely and securely within a barrel that is blackened and baffled to prevent stray light bouncing around from bright objects being viewed. This is why these things cost a lot of money - they are really precision optical instruments in their own right:

post-118-0-62445200-1344341594_thumb.gif

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