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variation in eyepiece design

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#1 jmillsbss

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Posted 16 May 2019 - 09:43 AM

Hey guys  -  Another newbie question.... please bear with.

 

I see there have been many different designs of eyepieces over the years.  ( Plossl, Nagler, Huygens, Erfle etc,)  some with 1 or 2 elements, some with 8 or 9 or more!  I get that they're named primarily for the designer, and I've seen layouts that show cross sections of each of the designs showing number of elements in the eyepiece.  Many of them are simply better designs from a previous design, where additional lenses have been inserted to correct specific inherent aberrations.  I understand there are high quality to low quality, expensive to low cost, in each of the designs, by the various manufacturers.  Coatings have improved over time.  But cost doesn't necessarily determine image/eyepiece quality.  Some company's plossl may be better than another company's Kellner (Just an example - EVERYBODY's Plossl may be better than the best Kellner! - No offense Kellner fans.)

 

So, are there better designs for viewing different types of objects?  Different designs best for splitting stars? Galaxies?  Nebulae?  Planetary?  I've got a box full of ES 82s in all different fl's, they're great for everything I've seen, but can a different design be better for a different target. Maybe the modern eyepieces have better glass and coatings, but I notice many of your signatures list many different brands AND designs of eyepieces.  You may not use them, but you list them!  

 

Perhaps the difference in fields of view or focal length are the only factors to consider but perhaps different eyepiece designs are important too.  Maybe not.  But I'm curious...

 

I already know... "Just get a box full of Ethos and you won't have to worry about it."  I'm asking a serious question here!

 

Like I said, I've seen the cross section comparisons, but if you've found a resource that shows best eyepiece design for different type target to view, please share.  Thank you!



#2 bobito

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Posted 16 May 2019 - 10:13 AM

I'm convinced that I can eek out a bit more detail on faint objects when using simple eyepiece designs versus wide fields.  I recall once switching between a 16mm Nagler and a 16mm Brandon on Whirlpool.  The difference in level of detail was obvious (to both me and a friend I was observing with).

I love the wide field EPs for their immersive and normally comfortable viewing.  But I spend more of my viewing time with simple Plossls, Orthos, and a few 3 element designs because I feel they provide better contrast.

 

(For context: My Wide Fields are mostly XWs, Naglers, and Panoptics.  Simple EPs are mostly TV Plossls, UO Orthos, TMB Monocentrics and AP SPLs).


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#3 J.LAMBIE

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Posted 16 May 2019 - 10:20 AM

What he said.



#4 MartinPond

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Posted 16 May 2019 - 10:39 AM

Even in the simpler designs, the precision,

polish, and stray light management count large.

 

Comparing a SVBONY Plossl and a TV, you will see 

more obsessive ribbing and baffling, and blowing up

the image, there is less of a "sandblasty" look to edges,

due to finer polish.

 

Looking through an older Zeiss or B&L Kellner  can be a sobering experience...

in terms of "I had no idea it could be this clean".  

 

There are excellent images at moderate prices, of course..

Getting a 25mm Celestron or Orion or Meade or GSO Plossl

gets a nicer image than a 12mm in the series....the relative scale

of the same size flaws is less with the bigger FL....the bigger lens

diameters and lower curvatures  even reduce the scratch/gouge.


Edited by MartinPond, 16 May 2019 - 10:40 AM.

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#5 rkelley8493

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Posted 16 May 2019 - 10:42 AM

The wide field eye-p's have more elements to expand the field. I think the Naglers incorporate a barlow of some type within the lens elements to give a much larger field of view than a simple plossl. Also, Mr. Nagler has a patented plossl design that corrects several common aberrations of the standard design, so a TeleVue plossl will probably have a better view than a plossl that comes with a telescope purchase. Also, the housing on a TeleVue plossl is much better quality, not just a thin piece of aluminum.

There are better designs for different types of objects, but the viewer is subjective. An orthoscopic eyepiece may have a brighter sharper image, but at the cost of a much smaller eye lens and tighter eye relief. I would much rather look through a large eye lens with long eye relief to get that "looking glass window" effect, no matter if the image may be "dimmer" or not, that doesn't matter to me. Comfort and preference does matter to me, but you won't know what you prefer until you try different options. 

I wouldn't recommend "getting a box of Ethos" unless you have the money to do it. They are top tier, but in my opinion, there are better choices out there [i.e. Explore Sci 92's]. Another case in point, 13 Ethos vs 14 ES 100. I prefer the 14/100, not that it's a better eyepiece, but it's more comfortable for me to use. Their performance is almost identical.


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#6 jmillsbss

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Posted 16 May 2019 - 11:21 AM

my intuition....less glass in the eyepiece, less times the light is redirected and, thus, possibly diminished, and there may be different types/qualities/finishes of glass that may have better transmission...



#7 rkelley8493

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Posted 16 May 2019 - 11:39 AM

my intuition....less glass in the eyepiece, less times the light is redirected and, thus, possibly diminished, and there may be different types/qualities/finishes of glass that may have better transmission...

In my experience, 1.25" eye-p's [10mm & under] seem to have a better image than that of 2" eye-p's of similar focal length. Barrel size aside, more to do with design. Case in point, the 8.8mm Explore Sci 82 & the 9mm ES 100. The image thru the 8.8/82 was brighter and sharper to that of the 9/100. The 1.25's design are more compact [this one may have fewer elements, but I know Pentax XW's have several elements], and the light doesn't have to travel as far thru the lenses. I still preferred the 9/100 because of comfort & ease of use, larger eye lens & wider field.



#8 MitchAlsup

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Posted 16 May 2019 - 12:03 PM

https://www.telescop...t/eyepiece1.htm


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#9 havasman

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Posted 16 May 2019 - 04:08 PM

my intuition....less glass in the eyepiece, less times the light is redirected and, thus, possibly diminished, and there may be different types/qualities/finishes of glass that may have better transmission...

It happens to me too that intuition can often lead away from fact. It is way more complicated than lens count. Some considerations:

  • ease of use - I have used others' short focal length ZAO-II's and find the combination of no eye cup, tiny physical dimension and their precious nature (for their owners) renders them enough more difficult to use that I just do not favor them over a Delos/Ethos, XW, Delite style that is so much easier to get full use of.
  • coatings - really important, with modern developments having positive impacts (exceptions apparently include some of the old Japanese makes, Claves and Zeiss but we have little access to those)
  • glass formulae - again, a really big deal
  • polish - I think this is never adequately factored into our ep analyses. IME, ES100's generally fall short here, for instance.
  • aperture - Alvin Huey famously praised Orthos and the like as the most effective ep's for close inspection of exotic, difficult far-away galaxies and galaxy groups and their details with premium Dobs. I sometimes use Tak Abbe Orthos for those observations but struggle to find in my 16" f4.49 the level of differences he describes. Discussing this with my pal Allan who is familiar with Huey's contentions and with very large aperture Dobs, he reminded me that Huey included a chart in his original paper to illustrate how drastically the improved observing support afforded by the top rank minimalist ep's increases with apertures >24". That makes perfect sense. But I DO NOT wish to extend that principle to refractors. That way lies madness and conflict. lol.gif 
  • purpose - sometimes more FOV is best and without substitute

In short, I reject to argument that fewer lenses and/or lens surfaces is better by definition. Experience teaches me that it is not the case. Advances in optical science and materials technology have relieved us of that hierarchy. Light can now be bent with less impact to its integrity.


Edited by havasman, 17 May 2019 - 02:59 PM.

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#10 Jon Isaacs

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Posted 16 May 2019 - 04:18 PM

my intuition....less glass in the eyepiece, less times the light is redirected and, thus, possibly diminished, and there may be different types/qualities/finishes of glass that may have better transmission...

 

The other side of the coin is that the light is less likely to go where it belongs... 

 

The differences in eyepiece transmission and contrast are subtle.  This is the eyepiece forum so one might expect this to be the mecca those who focus on those subtle differences.  That's not me.  A good set of eyepieces , some decent telescopes of appropriate apertures and observe every possible moment.. 

 

From the ATM's bible:

 

"It is not usually made clear, that these elements, objective and eyepiece, are by no means comparable in importance. The astronomer's hopes are almost wholly tied to the size and quality of the objectve. The objective of even the smallest telescope, because of its larger dimensions, the severe optical requirements it must meet, and the difficulty of its construction, completely overshadows the eyepiece."

- "How to Make a Telescope," by Jean Texereau, Page 1, Paragraph 2. "

 

Jon


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#11 MartinPond

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Posted 17 May 2019 - 12:25 PM

I'm convinced that I can eek out a bit more detail on faint objects when using simple eyepiece designs versus wide fields.  I recall once switching between a 16mm Nagler and a 16mm Brandon on Whirlpool.  The difference in level of detail was obvious (to both me and a friend I was observing with).

I love the wide field EPs for their immersive and normally comfortable viewing.  But I spend more of my viewing time with simple Plossls, Orthos, and a few 3 element designs because I feel they provide better contrast.

 

(For context: My Wide Fields are mostly XWs, Naglers, and Panoptics.  Simple EPs are mostly TV Plossls, UO Orthos, TMB Monocentrics and AP SPLs).

 

Wide or simple?

I get the best of both worlds with some of the 

precision-molded glass aspherics I have lifted from

Japanese binocs.    The F5 performance varies, but one I got

is an 18mm 2,1 with 60 degrees afov , 95% sharp at F5, 100%a F10

Contrast is usually awesome.

There are also "late bloomers" (want a longer virtual barrel)

that are awesome at 65 and 70 degrees afov, F8 and up.

I use some with an  ES3X focal extender....

there is a subtle difference with a good barlow... the ES 3X

seems to leave the contrast completely unaffected.


Edited by MartinPond, 17 May 2019 - 12:26 PM.



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