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eye relief with 2" Hyperion eyepieces?

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#1 lamplight

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Posted 09 January 2013 - 12:31 PM

Hi

the other night brought out my XLT 102 refractor and had some fun. as its cold i tend to just pop an eyepiece in and use it for the night. I wanted to get some more time behind a 2" 5mm Hyperion. this was perhaps a bit too much magnification for the seeing, but only JUST, but thats not my question.. ;)

I noticed I had to take off my glasses and pretty much push my eye against the (already folded down) eyecup. I picked this EP up used when i saw it as I'd heard here they have long eye relief. I just looked it up and this 5MM EP is supposed to be 20mm. all of the other "long eye relief" eyepieces I have bought can be used with glasses. I looked up my Astro Tech Paradigm 12mm 1.25" and that one has 13mm. I just tested it again and I can see the full outer rim with glasses on. Then I tried the hyperion with its 1.25" adapter attached and sure enough the eye relief is better. I am not outside to verify but im sure the FOV is smaller too, but thats not my question either ;)

is there any way I can get that 20mm of eye relief with this 2" EP? I want to get a nice wide field 2" EP at some point and am wondering if Ill run into the same thing. Just looked at their 31mm and the eye relief is a shorter 18mm. The ES 82º has 21mm eye relief. im totally confused why im not getting the eye relief i wanted.

I looked up the specs of it and i dont quite understand all of the adapters and threading options for it. mine didnt come with a manual.

im including a pic with it attached as a 2" to my diagonal just in case theres something im missng that a picture will show.

Attached Files



#2 CJK

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Posted 09 January 2013 - 12:39 PM

From my reading, eye relief is related most closely to focal length and has nothing to do with the diameter of the eyepiece itself: shorter focal length EPs generally have shorter eye relief than longer focal length EPs.

Eye relief is measured from the last lens element -- perhaps there is an eyecup or spacer that could be removed?

-- Chris

#3 SteveG

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Posted 09 January 2013 - 02:22 PM

Eye relief has nothing to do with focal length, it has to do with eyepiece design. I'm not sure though why the OP isn't seeing the stated eye relief of this eyepiece.

#4 csrlice12

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Posted 09 January 2013 - 03:24 PM

and I'm stealing your idea of using your Orion 9X50 RACI!! That's the one Omni drawback--that cheap excuse for a finder scope. After I've tried it for awhile, if it works well, I'll have to order another.

#5 Tony Flanders

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Posted 09 January 2013 - 04:13 PM

Eye relief has nothing to do with focal length, it has to do with eyepiece design.


No, that's not quite true. For any given design, eye relief is proportional to focal length. So, for instance, a 32-mm Plossl has twice the eye relief of a 16-mm Plossl. Which is plain common sense if you think about it. A 32-mm Plossl is simply a 2X scaled-up replica of a 16-mm Plossl.

This breaks down for more complex eyepieces, which usually include a negative element in the front. Even so, eye relief almost always decreases with eyepiece focal length except in eyepiece lines that are specifically designed to preserve it.

I have to admit that I'm baffled by this particular eyepiece; putting a 5-mm eyepiece in a 2-inch barrel seems a little pigheaded.

For what it's worth, I don't trust most manufacturer's eye relief specifications farther than I can throw them. Some are patently false by any measure. Some neglect the fact that the eyepieces have raised edges that reduce the effective eye relief. And even in cases where I'm sure the eye relief is technically correct, I find that I need to put my eye considerably closer to see the entire field of view.

#6 GeneT

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Posted 09 January 2013 - 06:12 PM

Someone will post on how you can measure the eye relief of your eyepiece. Manufacturers sometimes overstate or inaccurately state the specifications of their eyepieces. Also, design specs of eyepieces will affect eye relief. You get enough eye relief to view with glasses with some of your eyepieces. I developed an eyepiece strategy so I could do all my viewing while wearing glasses. For Naglers, I need a minimum of 17mm of eye relief. Nineteen or 20 is better. If you can't get the eye relief you want or need with the eyepiece, then I recommend you return it.

#7 Jon Isaacs

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Posted 09 January 2013 - 06:18 PM

This breaks down for more complex eyepieces, which usually include a negative element in the front. Even so, eye relief almost always decreases with eyepiece focal length except in eyepiece lines that are specifically designed to preserve it.



Just to add a bit of explanation to what Tony has already said:

Eyepieces like the Hyperions that provide long eye relief in the shorter focal lengths are almost always negative-positive eyepieces, that is, they consist of a front section that is essentially an optimized Barlow (telenegative) followed by a "normal" magnifying eyepieces (positive).

So a 5mm Hyperion might consist of a 5X "Barlow" and a 25mm magnifying eyepiece, the net result would be an eyepiece with an effective focal length of 5mm but with about 20mm worth of eye relief.

Jon

#8 vinnie

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Posted 10 January 2013 - 01:37 AM

Hi

the other night brought out my XLT 102 refractor and had some fun. as its cold i tend to just pop an eyepiece in and use it for the night. I wanted to get some more time behind a 2" 5mm Hyperion. this was perhaps a bit too much magnification for the seeing, but only JUST, but thats not my question.. ;)

I noticed I had to take off my glasses and pretty much push my eye against the (already folded down) eyecup. I picked this EP up used when i saw it as I'd heard here they have long eye relief. I just looked it up and this 5MM EP is supposed to be 20mm. all of the other "long eye relief" eyepieces I have bought can be used with glasses. I looked up my Astro Tech Paradigm 12mm 1.25" and that one has 13mm. I just tested it again and I can see the full outer rim with glasses on. Then I tried the hyperion with its 1.25" adapter attached and sure enough the eye relief is better. I am not outside to verify but im sure the FOV is smaller too, but thats not my question either ;)

is there any way I can get that 20mm of eye relief with this 2" EP? I want to get a nice wide field 2" EP at some point and am wondering if Ill run into the same thing. Just looked at their 31mm and the eye relief is a shorter 18mm. The ES 82º has 21mm eye relief. im totally confused why im not getting the eye relief i wanted.

I looked up the specs of it and i dont quite understand all of the adapters and threading options for it. mine didnt come with a manual.

im including a pic with it attached as a 2" to my diagonal just in case theres something im missng that a picture will show.


Hi Matt

The Hyperions are not 2" EPs. Well in a way I guess that they are, but the nose piece that you screwed off is not just an adaptor for 1.25". It is a lens group. Baader originally marketed these as "Two Eyepieces in One" and later added the concept of 3 or more EPs in one with the addition of the so called "Tuning Rings".

To expand on what Jon has stated above. The Hyperion design is in fact a six element Erfle with a two element achromatic tele negative group (Called a "Smythe" lens, and often compared to a "Barlow" lens - same horse different jockey) added as a nose piece. The 5mm Hyperion is in fact a 22.5mm Erfle with a 4.5x Smythe. This results is a 5mm effective end result. The idea as Jon has already explained is to maintain characteristics of the Erfle design in a much shorter length than was originally intended. The primary benefit of the Erfle design is its wide (for its time) field of view ~ 65° or more, and secondarily its long eye relief.

Therefore complete with nose piece the 5mm Hyperion is a 5mm 1.25" EP, and without nose piece it is a 22.5mm 2" EP

However. Various manufacturers following this path have optimised their EPs in 1.25" mode. That is with the Smythe lens or nose piece if you like in place. Removal of the nose piece does indeed revert the EP to a 2" Erfle but in a somewhat compromised mode.

I have owned both the 5mm and 8mm Hyperions and with both I found that with the nose piece removed the performance fell away dramatically compared to dedicated 2" EPs. I'm suggesting that although the eye relief still remained quite reasonable, that the edge definition fell away dramatically and more importantly the position of eye placement became critical. Combined, these two factors lead to a tendency to want to place the eye closer to the Eye Lens (the lens closest to the eye) and therefore robbing one of usable Eye Relief

My Opinion. Keep your 5mm Hyperion and use it in its optimised mode. ie as a 5mm 1.25" with a nice 20mm Eye Relief and a tidy 68° AFOV. Great value for dollar 5mm EP. But if you are looking for the low power wide field views of a nice 2" EP then add a dedicated 2" EP to your collection.

Oh and be aware, as you are using a 2" diagonal. If you drop in a Hyperion in 1.25" mode into a 2" diagonal in 2" mode you may find that the nose piece actually makes contact with the diagonal mirror in some diagonals. Not good. And in any case if you do this you'll find that the nose piece causes quite some degree of internal reflection in the diagonal. Best to use a Hyperion in 1.25" mode in a 2" diagonal with the diagonal's 1.25" adaptor fitted (A 2" Diagonal in this way offers good mechanical support of what is a fairly heavy Eyepiece) or just use a 1.25" Diagonal.

HTH

#9 coopman

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Posted 10 January 2013 - 07:40 AM

I found that I had trouble focusing the Hyperions when used in 2" mode, so I now use them with a 1.25" to 2" adapter in my 2" diagonal. I have the Hyp. 8, 13 & 17mm and I can comfortably use them with my glasses on and they seem to provide close to 20mm of eye relief.

#10 TexasRed

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Posted 10 January 2013 - 08:22 AM

That's not a 1.25" adapter you removed. That's part of the eyepiece. Leave it on, and your eyepiece will work just fine.

#11 Jon Isaacs

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Posted 10 January 2013 - 08:30 AM

That's not a 1.25" adapter you removed. That's part of the eyepiece. Leave it on, and your eyepiece will work just fine.


:goodjob:

Jon

#12 howard929

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Posted 10 January 2013 - 09:24 AM

I'm curious about weather that's really a 5mm 2" EP. Do you know what size the field stop is?

#13 Jon Isaacs

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Posted 10 January 2013 - 09:43 AM

I'm curious about weather that's really a 5mm 2" EP. Do you know what size the field stop is?


Howard:

From reading this thread and having owned the 13mm version, it's not really a 2 inch eyepiece, it's a 1.25 inch eyepiece with a 1.25 inch-2 inch barrel. Something I missed but others caught was that the 1.25 inch inner section had been removed. That section contains the Barlow/Smyth lens and is important...

Jon

#14 howard929

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Posted 10 January 2013 - 10:04 AM

I'm curious about weather that's really a 5mm 2" EP. Do you know what size the field stop is?


Howard:

From reading this thread and having owned the 13mm version, it's not really a 2 inch eyepiece, it's a 1.25 inch eyepiece with a 1.25 inch-2 inch barrel. Something I missed but others caught was that the 1.25 inch inner section had been removed. That section contains the Barlow/Smyth lens and is important...

Jon


Thank you Jon, that's what I figured it was, 1.25". As for the OP taking it apart as it seems he did, I find the Hyperions to be too tricky with those tuning rings. I do enough fiddling around in the dark as it is with what I have, I'm glad I avoided them entirely.

#15 Jon Isaacs

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Posted 10 January 2013 - 10:54 AM

Thank you Jon, that's what I figured it was, 1.25". As for the OP taking it apart as it seems he did, I find the Hyperions to be too tricky with those tuning rings. I do enough fiddling around in the dark as it is with what I have, I'm glad I avoided them entirely.



Howard:

You don't have to mess with the rings.. But I see you have some nice ES 82 degree eyepieces, they are good eyepieces from what I hear. Pretty hard to go wrong with them, particularly if you factor in the cost.

Jon

#16 lamplight

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Posted 10 January 2013 - 11:44 AM

The Hyperions are not 2" EPs. Well in a way I guess that they are, but the nose piece that you screwed off is not just an adaptor for 1.25". It is a lens group. Baader originally marketed these as "Two Eyepieces in One"


This makes sense. it says right on the box "Barrels for both 1.25" and 2" built in. thats why i bought it. what i am taking off is the 1.25" barrel, although it does have a lens group in it.

i just noticed that if i use the 1.25" barrel the magnification jumps a TON (probably the actual 5mm equiv (200x, 1000mm scope). i also noticed just now that the eye placement becomes much narrower like when using a barlow , so whoever said that , there is some barlow action going on. also, with the 1.25" "adapter" on i can see the whole FOV's edge without difficulty if my head/eye is at the sweet spot (ie: specific distance from EP is narrow but at least it has generous Eye relief).

Like i said i used this with the 1.25" off all night and the views were gorgeous, i had to almost turn my head to see all around.

at 2": eye placement wasnt as crucial but it did have to be closer as with any high mag EP.

and later added the concept of 3 or more EPs in one with the addition of the so called "Tuning Rings".


yes. there is another section entirely that also unscrews which appears to be where youd put the tuning rings or use it for afocal.

To expand on what Jon has stated above. The Hyperion design is in fact a six element Erfle with a two element achromatic tele negative group (Called a "Smythe" lens, and often compared to a "Barlow" lens - same horse different jockey) added as a nose piece. The 5mm Hyperion is in fact a 22.5mm Erfle with a 4.5x Smythe.


ok that explains above,.. i was browsing at 44.44X without the 1.25" "adapter"/barlow/smythe. seems about right based on the daytime test i just did.

design is its wide (for its time) field of view ~ 65° or more, and secondarily its long eye relief.
Therefore complete with nose piece the 5mm Hyperion is a 5mm 1.25" EP, and without nose piece it is a 22.5mm 2" EP

got it./ i never even noticed that as ive mostly used it at 2" so far.
so my FOV at 22.5mm seemed HUUUUGE.
How do i figure the FOV at 22.5mm? since it's marketed at 68º (at 5mm)?
if:
AFOV / MAGNIFICATION = FOV
would it be 68 / 44.44 = 1.53º ? thats SOUNDS right.

thanks for all the helpful posts not just this one.

anyone have a pdf manual for this specific EP? im curious about its other features for afocal and the tuning rings. their site is all in german and the english content is general.

thanks again

#17 newtoskies

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Posted 10 January 2013 - 11:50 AM

Matt, good thing you posted this question etc. I have learned a bunch from the advice, tips and suggestions given. Man there is a lot to learn still.

#18 Jeff2011

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Posted 10 January 2013 - 09:50 PM

This has been an interesting thread and has answered a lot of questions I had about my 13mm Hyperion. I was fascinated by the ability to remove the 1.25 nosepiece element but was not able to get it to focus until I got a 2" extender. The view was a bit stretched at the edges. I have attached a picture of the moon (with 1.25 element removed) I took using eyepiece projection with the adapter that lets you screw the eyepiece directly on to the camera t-ring adapter. This is a single image and the overall quality is good, but the moon looks a bit egg shaped.

Attached Files



#19 howard929

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Posted 11 January 2013 - 07:07 AM

I'm wondering if removing the 1.25" section with whatever lens group/s it contains also removes the field stop? Possibly the views appear egg shaped because you're seeing a wider but partial view which is other then what Baader intended.

#20 Midnight Dan

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Posted 11 January 2013 - 07:33 AM

... also, with the 1.25" "adapter" on i can see ...


Hi Matt:

Just want to re-iterate what others have said, that the 1.25" section is NOT an adapter. It is part of the eyepiece and normally should NOT be removed, even if you use it in a 2" diagonal.

Just leave the eyepiece fully assembled and insert it into either a 1.25" or a 2" diagonal. It will work as designed in that configuration.

While you *can* remove the 1.25" barrel and lens group and use the eyepiece as a 22mm (which sounds like what you were doing), I would not recommend that. The views suffer and it is not optimized for that configuration. If you need a larger view of the sky, you're much better off buying a longer focal length eyepiece.

-Dan

#21 howard929

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Posted 11 January 2013 - 07:40 AM

... also, with the 1.25" "adapter" on i can see ...


Hi Howard:

Just want to re-iterate what others have said, that the 1.25" section is NOT an adapter. It is part of the eyepiece and normally should NOT be removed, even if you use it in a 2" diagonal.

Just leave the eyepiece fully assembled and insert it into either a 1.25" or a 2" diagonal. It will work as designed in that configuration.

While you *can* remove the 1.25" barrel and lens group and use the eyepiece as a 22mm (which sounds like what you were doing), I would not recommend that. The views suffer and it is not optimized for that configuration. If you need a larger view of the sky, you're much better off buying a longer focal length eyepiece.

-Dan


Dan, good points.

I don't own any Hyperions, I was just trying to figure out why that 13mm did what it appeared to do after it was partially taken apart and used.

#22 Heitman

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Posted 11 January 2013 - 09:22 AM

Hello,
I agree with Dan, use it as a 5mm ep. I've also tried this, and while it was useable without the bottom lens group, the views definitely suffered.

Tim

#23 Midnight Dan

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Posted 11 January 2013 - 09:50 AM

Dan, good points.

I don't own any Hyperions, I was just trying to figure out why that 13mm did what it appeared to do after it was partially taken apart and used.


Oooops! Sorry, Howard! I started my post with "Hi Howard" but meant to say "Hi Matt". I wasn't responding to your post. :p I went back and changed it so it's correct now.

-Dan

#24 lamplight

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Posted 11 January 2013 - 10:30 AM

Hi

i knew you meant hi matt.

heres an overview from baader i found,
hyperion brief description (pdf)
of whats to be used and how it can and should not be disassembled. it makes more sense to me now in regard to everything explained here. i really have not seen a degradation in quality at the 22.5 focal length, so that is a bit perplexing that everyone is saying i "shouldnt do that". and their material says its designed to do that. it is a weird product , i didnt know what i was getting into. at least now its crystal clear whats going on so thanks! it will be interesting to do some testing with this in different scopes with clearer skies as well..its been high humidity all winter it seems.. a glare to the air..anyhow, super informative thanks!

#25 newtoskies

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Posted 11 January 2013 - 10:44 AM

That's a great link Matt. Made this much clearer for me now, and can follow what's being said here.

oh, my scope arrives today ...gonna be a fun weekend.






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