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Eyepiece Recommendations for 90mm Refractor

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#51 Sarkikos

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Posted 18 January 2014 - 02:21 PM

I have owned and used Delos 4.5 and 6, and XW's 3.5, 5, 7, 10 and 20. To my eye, the most obvious and immediate difference between the Delos and XW was the ease of finding and maintaining the best eye position with the XW compared to the relative difficulty in doing so with the Delos.

IME, the XW's were just easier and more comfortable to use right out of the box. Not so with the Delos. IMO this is why TeleVue has made such a point to get the eyeguard right, in order to help the observer set the optimal position for viewing through the Delos. This was also a big deal with the Radians and their Instadjust design.

That said, I still own a Delos 4.5. I've sold all my XW's since acquiring a Leica ASPH and Ethos-SX 3.7. But I wanted to keep at least one of TeleVue's latest and greatest. After all, there is that point about high light transmission for the Delos.

Mike

#52 John Anthony

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Posted 18 January 2014 - 03:12 PM

I have owned and used Delos 4.5 and 6, and XW's 3.5, 5, 7, 10 and 20. To my eye, the most obvious and immediate difference between the Delos and XW was the ease of finding and maintaining the best eye position with the XW compared to the relative difficulty in doing so with the Delos.

IME, the XW's were just easier and more comfortable to use right out of the box. Not so with the Delos. IMO this is why TeleVue has made such a point to get the eyeguard right, in order to help the observer set the optimal position for viewing through the Delos. This was also a big deal with the Radians and their Instadjust design.

That said, I still own a Delos 4.5. I've sold all my XW's since acquiring a Leica ASPH and Ethos-SX 3.7. But I wanted to keep at least one of TeleVue's latest and greatest. After all, there is that point about high light transmission for the Delos.

Mike


I experienced the same with the Pentax XL's compared to the Delos, Pentax was very comfortable to use, this is not say the Delos was problematic, the difference for me was slight but noticeable. I still feel overall the Delos was slightly a better performer then the Pentax XL, the Pentax imparting a somewhat warmer tone and the Delos with better light transmission.

#53 Sarkikos

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Posted 18 January 2014 - 09:47 PM

I had an XL 5.2 for a short time, but soon replaced it with an XW 5. The Pentax XW's were neutral toned. My LVW 8 was a little warm by comparison. The Delos so far seem about as neutral as the XW's.

Many eyepieces seem a touch warm when compared to the Pentax XO's. When viewing Jupiter, my Leica ASPH has a slightly warm tone in comparison to the XO's. But when I compared my Leica to the XW, they both seemed neutral. IME, the XO's appear neutral-to-cool.

On the other hand, TV Plossls are just obviously warm when viewing Jupiter or the Moon. I don't need to compare them to other eyepieces to see that.

Mike

#54 ibase

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Posted 18 January 2014 - 10:07 PM

And just like the results in Alvin Huey's big scopes field tests for threshold objects, the ranking by the French lab tests dovetailed the same pecking order:

1. Delos (best)
2. Ethos
3. Pentax XW

Parallel conclusions on optical prowess which matter most (without prejudice to other criteria) - both laboratory & big-scope field tests concurred that Delos is the best widefield; just because one couldn't tell the difference in small scopes doesn't mean that the difference doesn't exist and thus a toss-up, it's simply that the scope being used is not big enough in this case.

Best,


My guess is that it would take a night with excellent seeing using a top notch scope and an exceptional observer to see the transmission and contrast differences in those three eyepieces. Most of us fall short on one or two of the above requirements on any given night.


Agree.

Best,

#55 ibase

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Posted 18 January 2014 - 10:16 PM

To my eye, the most obvious and immediate difference between the Delos and XW was the ease of finding and maintaining the best eye position with the XW compared to the relative difficulty in doing so with the Delos.


Here's the other side of the coin - just like another forum member who recently posted here, Delos was better at beaning/blacking out control than Pentax XW. That's why mentioned earlier in the thread being quite happy trading the Pentax XW previously owned to get the Delos, which to my eye is less prone to beaning or blackouts (comparison with eyecups fully retracted). With the Pentax XW, just a slight off-than-optimal eye position would trigger the bean right away, whereas with the Delos, the leeway is wider, thus resulting in a less constrained head/eye position that's more forgiving of lateral movements, and ultimately more comfortable to use.

Another factor to consider is that if one has been using the Pentax XW for some time already, then tests a new Delos, more likely than not the Pentax XW will be judged better for eye-placement; give the Delos some time maybe, for a more equal comparison.

Best,

#56 Sarkikos

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Posted 19 January 2014 - 10:33 AM

Here's the other side of the coin - just like another forum member who recently posted here, Delos was better at beaning/blacking out control than Pentax XW.


I know there has been some controversy about this. Some observers say the exact opposite about Delos vs XW. Some say Delos control beaning/blackout better, others say the XW do.

Well, I have a Delos 4.5 and I can tell you that it has terrible beaning/blackout control - to my eye - compared to the performance of XW's. My Delos 6 was the same way. I just now put the Delos 4.5 up to my eye and could very easily shift the exit pupil out of the sweet spot. If I move my eye just a touch up, down, left or right, I see beaning and blackouts. I had an Orion Epic ED-2 22mm - eyepieces supposedly prone to beaning/blacouts - and it did not have more beaning/blackouts than the Delos.

That's why mentioned earlier in the thread being quite happy trading the Pentax XW previously owned to get the Delos, which to my eye is less prone to beaning or blackouts (comparison with eyecups fully retracted).


This has not been my experience at all. I certainly did not sell my XW's because of beaning/blackouts. I was very satisfied with how the XW's control those problems. I sold my XW's for two reasons: (1) redundancy with the Leica ASPH and other eyepieces; (2) dislike of switching among a series of eyepieces when viewing objects.

With the Pentax XW, just a slight off-than-optimal eye position would trigger the bean right away, whereas with the Delos, the leeway is wider, thus resulting in a less constrained head/eye position that's more forgiving of lateral movements, and ultimately more comfortable to use.


This is the exact opposite of my experience. Switch "XW" with "Delos" and you will have my experience.

Another factor to consider is that if one has been using the Pentax XW for some time already, then tests a new Delos, more likely than not the Pentax XW will be judged better for eye-placement; give the Delos some time maybe, for a more equal comparison.


Yes, I think much of this difference in experience might boil down to ... a difference in experience. We are discussing phenomena, not facts. :shrug:

But I do recall taking each XW out of the box, putting it up to my eye - and later using it in the field - and not having any problem at all with beaning/blackouts. Maybe other eyepieces I had used previously had somehow preconditioned me to an easy transition to the XW's. On the other hand, maybe my previous experience had not prepared me for the Delos.

In any case, I cannot honestly say that - to my eye - the Delos is very forgiving of eye position. I just don't see it. I was the same way about the Radians. I think it's a TeleVue thing. I tell you that is why they have put so much effort into designing their eyeguards and pupil guides - because of problems their customers have had with eye positioning. Seems obvious to me. They need to compensate for the eye positioning problems. Though I've never had a problem with the TV Plossls. A different animal entirely.

But then again, it could be a case of what I am - or am not - accustomed to. And of course the same could be true of observers who have had the opposite experience with Delos vs XW's.

Mike

#57 ibase

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Posted 19 January 2014 - 10:58 AM

I know there has been some controversy about this. Some observers say the exact opposite about Delos vs XW. Some say Delos control beaning/blackout better, others say the XW do.


Exactly; at least the viewers know there are two sides of the coin on this matter, and that we agree to disagree. :)

Best,

#58 Starman1

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Posted 19 January 2014 - 11:16 AM

Mike,
Said issues are usually the result of:
--exit pupil. Small exit pupils on long eye relief eyepieces often combine to yield difficulties in head positioning. This was probably the issue with the Radians.
--inability to hold the head steady. This varies a lot from individual to individual. People who stand (big dob users or SCT users with tripods all the way up) often have more problems with blackouts than people who sit.
Even despite that, it also varies from person to person. I had a 22T4 Nagler, an eyepiece a lot of people had problems with, but I could use it with the eyecup all the way down and never experience blackouts. Part of that was the larger exit pupil in the scope (~4mm) and part of that was that I was a lot younger and steadier then.
--Actual eye relief with the eyecup in place. It's been my experience that the XWs eyecup, even in minimum position, is taller than the eyecup on the Delos in minimum position. Either way, though, once the eyecup is adjusted to the right height, neither the XW nor the Delos should be hard to use or suffer from blackouts. Unlike other long eye relief eyepieces where the eyecup simply can't be raised high enough, on both XWs and Delos EPs, the eyecup CAN be raised high enough for even the perople who like to nestle their eyes into the eyecups.

Other than that, neither the Delos nor the XW suffers from spherical aberration of the exit pupil, so neither should experience "kidney beaning".

It's interesting that not every observer finds long eye relief to be a wonderful thing. Over the years, I've found my optimum is about 12mm of eye relief--longer becomes hard to use and/or shield the eye from peripheral light; shorter yields too much eyelash oil on the lens and too easy fogging in colder weather.

What I'm finding recently is that different eyepieces with highly concave eye lenses reflect peripheral light right into your eye. These eyepieces have to be used with a hood or by cupping the hands around the eyepiece. Yet, strangely to me, many observers don't notice this at all.

Optical quality is there. Now let's see some improvements in ergonomics of use.

#59 BillP

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Posted 19 January 2014 - 01:46 PM

I would add to your list:

- physiological differences in each observers eyes may help or hinder the situation

- how close the exit pupil of the telescope-eyepiece combination is to the dilation of the observer's pupil (when both are close to same then smallest head movement causes issue).

- actual specifics of the exit pupil design of the eyepiece. e.g., the design can place the exit pupil formation at specific places within the eye - Link .

#60 Sarkikos

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Posted 19 January 2014 - 02:34 PM

Optical quality is there. Now let's see some improvements in ergonomics of use.


As well as ergonomics of design.

Mike

#61 Starman1

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Posted 19 January 2014 - 06:19 PM

I would add to your list:

- physiological differences in each observers eyes may help or hinder the situation

- how close the exit pupil of the telescope-eyepiece combination is to the dilation of the observer's pupil (when both are close to same then smallest head movement causes issue).

- actual specifics of the exit pupil design of the eyepiece. e.g., the design can place the exit pupil formation at specific places within the eye - Link .

Well, how relevant those systems are that place the exit pupil differently than a typical telescope + eyepiece is debatable.

But, the article does point out some of the points I've often made about ultrawide fields and exit pupil, i.e. if the exit pupil is large enough (large enough % of the actual eye pupil diameter), looking at the edge of the field of view without rolling the head will result in vignetting (in this case, blackouts on one side of the field,which the article points to as a source of vignetting).
The technique of rolling the head while holding the pupil of the eye coincident with the exit pupil of the eyepiece is a learned behavior.
It must be instinctive in some users, and very hard to learn in others, judging from the varying reactions to ultrawide eyepieces.

Also, I am not near-sighted and many very myopic people report different issues with using eyepieces than those with average vision. Being myopic places the exit pupil and focus at different places, and this could cause exit pupil issues as well.

Truly, there are a host of physiological factors that could easily influence a person's reaction to a given eyepiece.

#62 Starman1

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Posted 19 January 2014 - 06:32 PM

Optical quality is there. Now let's see some improvements in ergonomics of use.


As well as ergonomics of design.

Mike

That brings up some questions:
--is long eye relief really better if you don't need to wear glasses to view?
--how well does the design block peripheral light?
--can eye relief be too short?
--what is the optimum eye relief?
--how well does the eyepiece block light from entering that is outside the exit pupil, or does it?
--how adjustable is the eyecup?
--why do some eyepieces have shiny anodized cylindrical surfaces above the eye lens instead of a flat black knife edge?
--why do some LER eyepieces have only a short eyecup?
--why do some short eye relief eyepieces have roll-up eyecups, or even eyecups at all?
--why do tiny, lightweight, eyepieces have safety grooves cut in their barrels?
--why do some designs have concave eye lenses of just the right curvature to allow peripheral light to reflect into the eye?
--why do some eyepieces have issues with reflections from the cornea while others don't?
--why are the bottoms of most eyepieces shiny and reflective?
--how can an ultrawide field eyepiece be constructed so that users don't have issues with seeing the edge?
--could ultrawide field eyepieces be constructed with long eye reliefs?
etc., etc.

I really don't think we're at the end of design in eyepieces.
However, if light pollution is not controlled, the visual use of telescopes may precipitously decline, and this could make further development of eyepieces commercially unviable.

#63 Sarkikos

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Posted 19 January 2014 - 09:13 PM

--how can an ultrawide field eyepiece be constructed so that users don't have issues with seeing the edge?

--could ultrawide field eyepieces be constructed with long eye reliefs?
etc., etc.


If these design problems can be solved, I predict a tsunami wave of sales in ultrawide field eyepieces. :ubetcha:

I really don't think we're at the end of design in eyepieces.
However, if light pollution is not controlled, the visual use of telescopes may precipitously decline, and this could make further development of eyepieces commercially unviable.


There are always the bright planets and the Moon, and double stars to some extent. Deep sky isn't all there is.

Mike

#64 Starman81

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Posted 19 January 2014 - 10:26 PM

In the Delos vs XW debate, overall, I am more in Mike's (Sarkikos) camp with my experience. I had the 10 Delos previously and tested it out vs the XW 10 which was already entrenched in the lineup. Yes, the Delos was a little bit of an effort to hold the exit pupil but it was still very comfy. The XWs were the incumbents and there wasn't enough of a case to replace them with Deloi.

Most recently though, I've tried the 17.3 and 14 Deloi. They were so comfortable to use, I started thinking that I was perhaps a bit quick to dismiss the 10 Delos. Then I realized that it might be the larger exit pupils of these longer focal lengths. The 17.3 didn't fit my needs but I am thinking the 14 Delos will replace the XW 14. There is something very special about the Deloi, they seem much more immersive than the 72* AFOV would lead you to believe. Seems more like 82* with a ton of ER!

#65 Starman1

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Posted 19 January 2014 - 11:44 PM

--how can an ultrawide field eyepiece be constructed so that users don't have issues with seeing the edge?

--could ultrawide field eyepieces be constructed with long eye reliefs?
etc., etc.


If these design problems can be solved, I predict a tsunami wave of sales in ultrawide field eyepieces. :ubetcha:

I really don't think we're at the end of design in eyepieces.
However, if light pollution is not controlled, the visual use of telescopes may precipitously decline, and this could make further development of eyepieces commercially unviable.


There are always the bright planets and the Moon, and double stars to some extent. Deep sky isn't all there is.

Mike

Very true, but do you need ultrawides for them?

#66 Sarkikos

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Posted 20 January 2014 - 12:36 AM

But do you need ultrawides for deep sky?

No, not always. Arguably, not most of the time. I use my ES 100 14 for large DSO and large fields of multiple DSO. I use my Ethos-SX 3.7 for close-up views of planetaries and to see structure in some bright nebulae. Otherwise, the vast majority of faint fuzzies do fine in my Leica ASPH and Baader Zoom. For the really faint fuzzies, I put in an XO or Sterling Plossl.

Now back to the original question: Do I need ultrawides for bright planets and the Moon? Well, yes, they do come in handy for viewing these objects in my nontracking Dobs. And I think many Dob users buy ultrawides for those objects. A good ultrawide field high-power eyepiece in a Paracorr is a good alternative to simple glass eyepieces or even binoviewing. A good alternative, though admittedly perhaps not the best option.

Mike

#67 ibase

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Posted 20 January 2014 - 09:18 AM

There is something very special about the Deloi, they seem much more immersive than the 72* AFOV would lead you to believe.


Syed,

Am with you on this one. The really big eye lens of the Delos (~35mm diameter) coupled with the generous eye relief probably contributes to the more palpable immersion making the views look wider than the 72° AFOV.

Posted Image
Delos eye lens

Best,






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