#1  
Old 25-07-2020, 02:24 PM
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Stonius (Markus)
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TV eyepiece comparison?

I know it's mostly to do with apparent FoV and eye relief, and it also depends upon the scope, BUT!


Are there any general consensuses? consensi? on the differences above and beyond that?


Current range with AFoV goes



Plossl (50)

DeLite (62)

Panoptic (68)

Delos (72)

Nagler (82)

Ethos (100)



Surely an Ethos isn't just a wider Nagler. Do they publish any data astigmatism, field curvature, aberrations and the like?


Would you for example, expect a Delos to have better on-axis performance than an Ethos? Are DeLites more for planetary observing like the Plossls?



Cheers


Markus
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  #2  
Old 25-07-2020, 03:33 PM
Startrek (Martin)
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From my experience with TV eye pieces, each type has a different viewing experience for specific objects and seeing conditions. I have Panoptic, Delite, Delos, Ethos and Apollo 11
If I had to select one TV eye piece out of the whole range to use for the rest of my days on all objects it would be the Panoptic 27mm, a simply beautiful eye piece
They all have been designed for specific astronomical purposes, price range and user comfort
Although my least favourite would be the Delite range which I believe are more suited for the budget minded astronomer who want to get into TV or for Bino use.
I have astigmatism in my right eye so purchased a TV Dioptx accessory and found it worked with varying degrees of success. Now days I just observe with my left eye which just has myopia.
It’s a shame these eyepieces are out of the price range for a lot of folk as they are well engineered and designed high quality optical instruments
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Old 26-07-2020, 12:58 PM
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The Apollo 11 is a bit of a mystery to me. The spec sheet says it has 0 lenses in 0 groupings!


Is it just a Nagler, or is it a completely new design?
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Old 26-07-2020, 01:27 PM
Startrek (Martin)
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The design and construction of the optics in the Apollo 11 eye piece is a bit of a mystery and so it should be ( only 300 made ) I’ve never owned a Nagler but have observed through a few so can’t compare
Here’s my first review of the Apollo 11 eye piece a few months ago it your interested -

Televue Apollo 11 Commemorative eye piece review ( 6th May 2020 )

With a 95% waxing moon passing the north meridian at good altitude I decided to use my Apollo 11 eye piece for only the third time this year and report on my experiences during lunar observations

Apollo 11 eye piece Specifications
Serial no 186
AFOV 85 degrees
Focal length 11mm
Eye relief 18mm
Field Stop 16.2mm
2” and 1.25” barrel
Length 138mm
Weight. 2” is 620gm and 1.25” is 526gm

Scope used
Skywatcher 12” f5 Goto dob
Focal length 1500mm

My eye condition
I wear glasses but choose to observe without glasses
Left eye - myopia
Right eye - myopia with astigmatism 1.5 diopter

Filter
Orion 2” variable polarising filter 1% to 40% transmission ( set to approx 30% )

Sky Conditions
Bortle 3
Clear no cloud present
Light westerly wind at 3 knots
Seeing average to good
Transparency good

Viewing comfort
With an eye relief of 18mm this eye piece was very comfortable to use. It has a large 30mm diameter of glass and a generous rubber eye guard ( 9mm depth) at the observing end
Bringing my eye to the eye piece and close to the rubber guard I experienced no kidney beaning or black outs

Optical Performance
Centering the 95% waxing moon in the eye piece, I could fit the whole planet just inside the AFOV
After fine focus I observed both off axis and on axis regions and experienced no field curvature or distortion
The colour and contrast across the field was uniform with little or no noticeable aberration

Moving across to different regions of the moon the views were sharp and consistent and as expected improved at the edges against the blackness of space where the profile of craters and mountains were accentuated by the backdrop

Summary
Having used Televue eye pieces namely Delites, Panoptic, Delos and Ethos for the past 4 years in various size scopes ranging from 6” to 12” you tend to expect a high level of performance from these quality eye pieces and the Apollo 11 commemorative eye piece is no different. It is a superb quality eye piece and definitely not a show piece for a cabinet. Although I’ve only used it on a limited number of objects , my recent lunar observations exceeded my expectations and I look forward to other planetary observations ( Jupiter and Saturn ) in the coming months.I would be most interested to see how this eye piece performs with a Powermate should conditions allow. Before finishing up for the night I popped my Delos 10mm eye piece in to gauge some comparisons with the Apollo 11 and although the Delos views were superb , I found the Apollo 11 refreshingly different and pleasing to the eye.The 85 degree AFOV gave the Apollo 11 eye piece a bit more “wow factor”

The above review is an individual observation based on one celestial object only and by no means comprehensive and maybe different from observer to observer

Cheers
Martin
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Old 27-07-2020, 01:28 AM
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Here are a couple links where the Ethos and Delos are members of a group of elite eyepieces that are lab and field tested.:
https://web.archive.org/web/20110622..._oculaires.pdf
https://web.archive.org/web/20130829...aires_10mm.pdf
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Old 31-07-2020, 03:25 PM
jamespierce (James)
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The FOV is the only major difference any normal user will detect between all the eye pieces. Teleview really doesn't make any bad eyepieces. If you are really pushing the limits of visual observing, among the very serious deepsky observers I know the Ethos are broadly regarded to have the best coating and contrast (and a price to match). Personally I own some Nagler and some Ethos and use the ones that match the scopes best. That's a more important factor.
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Old 02-08-2020, 08:17 AM
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Quote:
Originally Posted by Stonius View Post
I know it's mostly to do with apparent FoV and eye relief, and it also depends upon the scope, BUT!


Are there any general consensuses? consensi? on the differences above and beyond that?


Current range with AFoV goes



Plossl (50)

DeLite (62)

Panoptic (68)

Delos (72)

Nagler (82)

Ethos (100)



Surely an Ethos isn't just a wider Nagler. Do they publish any data astigmatism, field curvature, aberrations and the like?


Would you for example, expect a Delos to have better on-axis performance than an Ethos? Are DeLites more for planetary observing like the Plossls?



Cheers


Markus
Some eyepiece measurements:
http://astro-talks.ru/forum/viewtopi...&t=1483#p41976
http://astro-talks.ru/forum/viewtopic.php?f=7&t=1897

I'll answer your questions directly:
1) Is there any general consensus on the differences above and beyond that?
The lines have different eye reliefs, important to many people, and the differences in apparent field are important in particular scopes, and different people prefer different eyepieces. TeleVue tries to make the feel identical across a line, but they only mostly succeed. Different focal lengths in a series always seem to get higher accolades. They differ in performance across a line as the above links show.
2) Surely an Ethos isn't just a wider Nagler. Do they publish any data astigmatism, field curvature, aberrations and the like?
No one publishes such data. Pentax did once a long time ago and the data is still available on the web wayback machine, but generally such information is proprietary and not released to the public. Lab tests to reveal the data you mention don't, by and large, exist in the astronomy market because the market is too small to pay for such tests and because most amateurs don't have the knowledge to interpret the results. not to mention that it might kill sales for a particular eyepiece if such data were known.
The Ethos is not a Nagler--it has more elements and different correction. It's a more sophisticated design, and possible only because of advancements in coatings.

3)Would you for example, expect a Delos to have better on-axis performance than an Ethos?
As I mentioned, eyepieces vary across a line. Not all Delos are equal. Not all Ethos are equal. However, the spot sizes for axial images say that any differences seen are likely to be due to seeing conditions. Everyone asks about on axis views, where the differences between eyepieces are minute. It is the edge of the field where the major differences between eyepieces exist.
4)Are DeLites more for planetary observing like the Plossls?
Plössls and Delites are general use eyepieces, not just for planets. Plössls, in particular, don't go to short focal lengths for planetary use because the eye reliefs get too tight. Delites were created to have vanishingly small spot sizes across the field and offer glasses-friendly eye relief to 3mm. They are TeleVue's "planetary" eyepieces if you prefer shorter focal lengths and narrower fields for planets. I favor the 3.7mm Ethos SX for Uranus and Neptune because the scope is a dob and at 500x, the objects drift across the field very fast. in my case, the Delite is too narrow for that. But they work fine in my 4" apo, which has a much shorter focal length.
But they work just fine as general deep sky use eyepieces in most telescopes. The 62° field of view works well for ease of use, and yields adequately large true fields in short focal length scopes.
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Old 02-08-2020, 08:22 AM
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Quote:
Originally Posted by Stonius View Post
The Apollo 11 is a bit of a mystery to me. The spec sheet says it has 0 lenses in 0 groupings!


Is it just a Nagler, or is it a completely new design?
A completely new design. It has long eye relief at 85°. I use mine with glasses. The only way to know the lens count is to dismantle one. Feel free. I don't intend to do so.
TeleVue will likely never share that data with us.
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  #9  
Old 02-08-2020, 10:25 AM
astro744
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Tele Vue has a lot of information about the virtues of each eyepiece design on their website. Click on background tab for each eyepiece type.

E.g. For Delos,

http://www.televue.com/engine/TV3b_p...=183&Tab=_back

Eyepiece specifications at;

http://www.televue.com/engine/TV3b_page.asp?id=214

Scroll down for discontinued models.
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Old 02-08-2020, 07:29 PM
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" It is the edge of the field where the major differences between eyepieces exist."


Thanks for that very informative post, Don. Would it be true then to surmise that edge of field performance will be worse the wider the AFoV is? (not just for TV, but for any EP?)


Cheers
Markus
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Old 02-08-2020, 07:32 PM
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Quote:
Originally Posted by astro744 View Post
Tele Vue has a lot of information about the virtues of each eyepiece design on their website. Click on background tab for each eyepiece type.

E.g. For Delos,

http://www.televue.com/engine/TV3b_p...=183&Tab=_back

Eyepiece specifications at;

http://www.televue.com/engine/TV3b_page.asp?id=214

Scroll down for discontinued models.



I have looked at those pages, but I know there is often a gap between reality and the marketing department's superlatives. So I was more looking from the folk wisdom from real users
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Old 02-08-2020, 07:39 PM
jamespierce (James)
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No I don't think it's as simple as that.

There is a reason the Ethos cost as much as they do!

I'd say more crudely like all optical systems (thinking camera lenses etc as well) newer computer aided design techniques have probably had a greater impact at the edges than in the centre.

Something I did miss in my earlier comment is eye relief, I'm not a glasses wearer so it doesn't impact me much until you get down to very short focal length plossel etc.

As with most things you do get what you pay for, IMHO the biggest mistake with eye pieces is having too many. Better to have 2 or 3 great eyepieces than 10 ok ones.

Buy three:
  • Widest field you can get with your scope and maintain a ~5-6mm exit pupil.
  • Something which gives a 1-2mm exit pupil (this will be the sweet spot of the scope and your eyes ... should be your most used eyepiece).
  • Something which gives you ~200-250x for planets and nights of good seeing. Not often that usable in Australia.
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Old 02-08-2020, 07:42 PM
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Strangely enough, that's the reason behind this whole post. I'm thinking of cross-grading to just three really good eyepieces, and I was thinking of exactly the configuration you mention. :-)
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Old 04-08-2020, 06:57 AM
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Quote:
Originally Posted by Stonius View Post
" It is the edge of the field where the major differences between eyepieces exist."


Thanks for that very informative post, Don. Would it be true then to surmise that edge of field performance will be worse the wider the AFoV is? (not just for TV, but for any EP?)


Cheers
Markus
Not necessarily. There are poor 70° eyepieces and superb 100° eyepieces.
It does seem , however, that the wider the field the more it costs.

One other concern is the f/ratio of the scope. Correcting an eyepiece for a fast light cone requires more lenses and a different design than designing the eyepiece for f/8-f/10. And cost sometimes relates to how well corrected the eyepiece is at fast f/ratios.
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Old 04-08-2020, 06:59 AM
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Quote:
Originally Posted by Stonius View Post
Strangely enough, that's the reason behind this whole post. I'm thinking of cross-grading to just three really good eyepieces, and I was thinking of exactly the configuration you mention. :-)
I found that if the fields are 100°, you can have bigger jumps between focal lengths and get away with it.
In 100°, for instance, a 21mm, 13mm, 8mm could be a set or 17mm, 10mm, 6mm. That would depend on the focal length of the scope.
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