TV Delos Owners??

[issdaol (Phil)]

Hi All,

Was just wondering if anyone has any experience using TV Delos EP's??

Are these a significant improvement over Nagler & Ethos but just with less FoV and greater Eye Relief??

Was looking at a few options such as Pentax and Vixen and how they would compare??

Also anyone have any experience using TV Dioptrx?? How good is this? Are there better options out there?

Any advice/pointers appreciated

Cheers

[Rodstar (Rod)]

Hi Phil, I am interested to see what others have to say in response to your post as I am contemplating purchasing the longest focal length Delos (17.3mm).

The following appears on the Bintel website:

"Introducing Delos
Tele Vue is pleased to introduce the Delos, mid-to-short focal length line of 20mm eye-relief, 72° apparent field of view eyepieces. Every optical, mechanical, and ergonomic aspect was rethought to achieve reference-standard performance for any visual application.

The Delos was conceived as a narrower field Ethos. Reducing the field to 72° allowed freedom to increase eye-relief, while controlling pupil aberrations, all without making the eyepiece too large. With Ethos performance standards as benchmarks, the Delos design achieves full field sharpness, virtually perfect f ? (theta) distortion mapping, and color neutrality. Image fidelity is maximized utilizing glass matched multicoatings and anti-reflection surfaces throughout the eyepiece.

Contrast is further enhanced with a new, continuously adjustable height eyeguard system that can be locked in any position. Since the Delos eye-lens measures a quite large 35mm in diameter, preventing stray light from reflecting off the first surface and extraneous light from entering your eye pays off in a nice increase in perceived contrast. The eyeguard's sliding action allows for positioning the soft rubber eyeguard at the ideal height to suit the observer's preference. Indicator marks on the eyepiece body are handy reference guides for setting your perfect position. The eye-guard can also rotate for Dioptrx users."

[pgc hunter]

Type the following into Google Search:

site:cloudynights.com cloudynights delos

and it'll come up with several pages of Delos comparisons, observing reports and feedback from those that used it.

[MortonH]

I fancy the new 17.3mm one. The Delos line seems to be very good.

Morton

[issdaol (Phil)]

checked out the CN search as suggested, there are a few really good comments from some users that have swapped Pentax XW's for the Delos and some balancing less positive ones as well.

The difference does seem small though.

Some have commented that the Delo's is better than their Ethos.

Also a lot of comments from people that are just making assumptions but have not owned or do not own one.

Might be a little too early to tell apart from buying and giving it a go......

[ausastronomer (John Bambury)]

Originally Posted by MortonH

I fancy the new 17.3mm one. The Delos line seems to be very good.

Morton

The DELOS line only goes where the Pentax XW's went 9 years ago in terms of cool neutral colour tone, high light transmission, high contrast and high on axis sharpness. The first step Televue made to the cooler colour tone over their traditional offerings came with the 13mm ETHOS which was released in May 2007.

You're going to read a lot of reports on US internet forums about how the DELOS is better than the Pentax XW's. Your also going to read reports about how the difference beween them is minimal. Don't lose sight of the fact that Americans are a very patriotic race and very loyal to their own brands and a lot of those reports are not going to be as objective as they might be. I haven't used the DELOS yet but I have used the ETHOS countless times in a number of different focal lengths and in none of those focal lengths does the ETHOS outperform the equivalent focal length Pentax XW in terms of light throughput, contrast and sharpness. Their performance is extremely close, but if I had to split them, I would lean very slightly to the Pentax XW's. That is academic because I prefer more eye relief than what the ETHOS offers. I read countless internet reports on US forums about how this ETHOS and that ETHOS outperformed its Pentax XW equivalent, on such and such a target. That is just plain poppycock. There is barely a struck match between them. Credit to Pentax that Televue took 11 years to catch up as the Pentax XL's, which pre dated the XW's and are almost the same performance wise, were born in 1996; 11 years before the ETHOS. The DELOS line uses the same lens, glass and coating technology as the ETHOS so you can assume its performance will be almost the same as the ETHOS and the Pentax XW's, which BTW is very top shelf.

Cheers,
John B

[ausastronomer (John Bambury)]

Originally Posted by Rodstar

Hi Phil, I am interested to see what others have to say in response to your post as I am contemplating purchasing the longest focal length Delos (17.3mm).

Hi Rod,

I am not quite sure why you need to consider this eyepiece, unless you are also changing other things.

Am I correct in assuming you own a 13mm ETHOS and a 20mm T5 Nagler?

If so, in your scope (20"/F5 FL = 2550mm) these eyepieces give you the following True Fields of View and magnification

13mm ETHOS = .51 degrees TFOV @ 196X
20mm Nagler T5 = .64 degrees TFOV @ 128X

If you purchase the 17.3mm DELOS with its 72 deg AFOV it will give you

TFOV = .49 degrees @ 147X

Consequently you gain nothing in terms of TFOV. It gives a slightly reduced TFOV compared to your 13mm ETHOS at lower magnification, thus contrast and detail will be slightly reduced compared to the 13mm ETHOS. I can understand however that 147X may be a more usefull magnification for you under variable seeing conditions than the 196X of the 13mm ETHOS, which may not always be useable.

I think in your case the 17mm ETHOS would be a better choice, but this then bumps heads with your 20mm Nagler in terms of TFOV.

Maybe you need a lengthy discussion with SWMBO and tell her you should sell the 20mm Nagler T5 and buy the 17mm and 21mm ETHOI to go with your 13mm ETHOS

Cheers,
John B

[MortonH]

Originally Posted by ausastronomer

The DELOS line only goes where the Pentax XW's went 9 years ago in terms of cool neutral colour tone, high light transmission, high contrast and high on axis sharpness. The first step Televue made to the cooler colour tone over their traditional offerings came with the 13mm ETHOS which was released in May 2007.

You're going to read a lot of reports on US internet forums about how the DELOS is better than the Pentax XW's. Your also going to read reports about how the difference beween them is minimal. Don't lose sight of the fact that Americans are a very patriotic race and very loyal to their own brands and a lot of those reports are not going to be as objective as they might be. I haven't used the DELOS yet but I have used the ETHOS countless times in a number of different focal lengths and in none of those focal lengths does the ETHOS outperform the equivalent focal length Pentax XW in terms of light throughput, contrast and sharpness. Their performance is extremely close, but if I had to split them, I would lean very slightly to the Pentax XW's. That is academic because I prefer more eye relief than what the ETHOS offers. I read countless internet reports on US forums about how this ETHOS and that ETHOS outperformed its Pentax XW equivalent, on such and such a target. That is just plain poppycock. There is barely a struck match between them. Credit to Pentax that Televue took 11 years to catch up as the Pentax XL's, which pre dated the XW's and are almost the same performance wise, were born in 1996; 11 years before the ETHOS. The DELOS line uses the same lens, glass and coating technology as the ETHOS so you can assume its performance will be almost the same as the ETHOS and the Pentax XW's, which BTW is very top shelf.

Cheers,
John B

Hi John,

Absolutely agree that people may bias their reviews towards the "home team". I have an old Pentax XL 21mm and love it. Ironically it's about the only eyepiece I've never sold, while several Televues have come and gone over the years, although that was usually due to changing scopes and wanting other focal lengths.

I certainly don't think that TV eyepieces are better than the Pentax line, but TV are definitely top drawer and I think cheaper than Pentax. So if you factor in the price then Televue may arguably be the "best" of the premium eyepieces.

Going back to your main point, the differences noted in reviews probably reflects the differences in the reviewers themselves more than the eyepieces.

Bottom line, either will serve you well and it's great to have options.

Morton

[Fox]

There is one area where the Delos is likely to significantly differ in comparison to the Pentax XW line, and that is the field curvature issues encountered with the Pentax XW 14mm and 20mm eyepieces. I found the 14mm Pentax XW field curvature to be too severe for my liking in the f/5 Genesis. So I have a Vixen LVW 13mm instead; albeit I'm now seriously considering the Delos 14mm or Ethos 13mm to replace my Vixen (& I'm ranking the Delos 14mm as my likely favourite).

[Suzy]

Adoroma in the U.S. have the Pentax XW5, 7 & 10mm on sale at the moment for only $279, plus shipping ($60 to Qld)- that comes in at $330. It's the cheapest I've seen them so I couldn't resist jumping in and adding a 5mm to my XW collection.
OPT are still selling them for $360 plus shipping.

http://www.adorama.com/searchsite/de...info=pentax+xw

[Rodstar (Rod)]

Originally Posted by ausastronomer

Hi Rod,

I am not quite sure why you need to consider this eyepiece, unless you are also changing other things.

Am I correct in assuming you own a 13mm ETHOS and a 20mm T5 Nagler?

If so, in your scope (20"/F5 FL = 2550mm) these eyepieces give you the following True Fields of View and magnification

13mm ETHOS = .51 degrees TFOV @ 196X
20mm Nagler T5 = .64 degrees TFOV @ 128X

If you purchase the 17.3mm DELOS with its 72 deg AFOV it will give you

TFOV = .49 degrees @ 147X

Consequently you gain nothing in terms of TFOV. It gives a slightly reduced TFOV compared to your 13mm ETHOS at lower magnification, thus contrast and detail will be slightly reduced compared to the 13mm ETHOS. I can understand however that 147X may be a more usefull magnification for you under variable seeing conditions than the 196X of the 13mm ETHOS, which may not always be useable.

I think in your case the 17mm ETHOS would be a better choice, but this then bumps heads with your 20mm Nagler in terms of TFOV.

Maybe you need a lengthy discussion with SWMBO and tell her you should sell the 20mm Nagler T5 and buy the 17mm and 21mm ETHOI to go with your 13mm ETHOS

Cheers,
John B

Hi John, thanks for your careful analysis of my EP situation. I am aware of the various issues you raise, and have contemplated enlarging my Ethoi collection. Alas, I would prefer to spend my money on other things at this stage.

My interest in the Delos is not driven by what other EPs I may have in a similar focal length or TFOV, but rather the more intangible notion of "comfort". Part of this may be eye relief, but there can be other more subjective issues at play.

I adored my 22mm Panoptic and regret selling it. Notwithstanding its slightly inferior performance at edge of field, and narrower field of view (68 degrees) it was, for reasons which are perhaps a little hard to pin down, the most comfortable EP I have ever had. When I had it, it spent more time in the focuser of the Mary Rose than any other EP.

With my current line up, the 20mm Nagler plus Paracorr is my default observing choice. This renders an effective focal length of 17mm. While I love the 20mm Nagler, it does have fairly tight eye relief, which means that it is not optimally comfortable, and when glasses wearers share the views with me through the Mary Rose, it is definitely far from ideal for them.

I confirm that the 13 Ethos is not useful more often than not. The seeing in my area does not support 200x all that often. Having something in the 17mm area is a logical slot for me for times when the seeing is just not quite up to scratch for the 13E.

I am interested to know how the 17.3mm Delos may perform as an alternative. It might just be near dang perfect, for a pretty reasonable price that even SWMBO (aka the Minister for Finance) cannot argue with.

I am particularly interested to know how it performs without a Paracorr. If coma is an issue, then I will not be purchasing one.

[ausastronomer (John Bambury)]

Originally Posted by Fox

There is one area where the Delos is likely to significantly differ in comparison to the Pentax XW line, and that is the field curvature issues encountered with the Pentax XW 14mm and 20mm eyepieces. I found the 14mm Pentax XW field curvature to be too severe for my liking in the f/5 Genesis.

Hi Fox,

The noticeable field curvature of the 14mm and 20mm Pentax XW's is user and telescope dependant. Some users have a greater ability to accomodate and adjust for field curvature than others. Further, the observed field curvature is telescope dependant. Your F5 TV Genesis has a very short radius of curvature of the main objective and will "dramatise" the observed field curvature, notwithstanding that it is a petzval design scope with an inherently flat field. I spent quite a bit of time recently with both the 14mm and 20mm Pentax XW's in my 10"/F5.3 SDM and specifically looked for and compared the field curvature and off axis astigmatism of these eyepieces with several of my TV Naglers. It's worth noting that the observed field curvature of the eyepiece is dependant on the radius of curvature of the primary objective in combination with the eyepiece. It has nothing to do with the F-ratio of the telescope. That affects coma and off axis astigmatism. Whilst your TV Genesis has a similar F-ratio to my scope my scope has a "much" larger radius of curvature of the primary / objective. I could certainly detect some very minor field curvature in both the 14mm and 20mm XW's in the 10"/F5.3. When I tight focused in the center of the FOV on rich star fields in Scorpius (M6 and NGC 6231 regions) I could tell the EOF was just off best focus. This was minimal and not intrusive to the view, to my eye. Other people may have less focus adjustment in their eyes than I do. If I then tight focused stars 50% of the way to the EOF, the stars both in the centre of the FOV and at the EOF appeared tight focused, even though I could still tighten them a touch with the fine focus wheel on the Feathertouch. What I can tell you is that the EOF performance of the 14mm and 20mm Pentax XW's in this telescope was clearly superior to the EOF performance of both my 17mm and 22mm T4 Naglers. It wasn't even close. When combined with a paracorr and the paracorr properly adjusted for each eyepiece, they all performed superbly in this telescope with beautiful flat fields right to the EOF. In larger newtonians the 14mm and 20mm Pentax XW's get better and better, due to the longer focal length and radius of curvature of these scopes. In a telescope like a 20" or 25"/F5 these eyepieces perform beautifully, particularly when combined with a paracorr. They perform very well in both my 14"/F4.5 SDM and in my 18"/F4.5 Obsession. To the extent that I prefer the 14mm Pentax XW + Paracorr to the 13mm ETHOS + Paracorr.

I have to be honest I think the field curvature issues of these two eyepieces is way overplayed on most internet forums. Sure they struggle to perform in short focal length refractors due to the tight radius of curvature of the objective of these telescopes, but they do perform very well in telescopes having a longer focal length. When combined with a paracorr they perform superbly in just about all fast newtonians. You seriously can't just make a blanket statement that they have field curvature issues based on your experience in a small telescope with a very short radius of curvature. Funny how you never read about the off axis performance of the 17mm and 22mm Naglers, particularly when they are clearly outperformed in most decent sized visual telescopes by the 14mm and 20mm Pentax XW's.

The best advice I can give anyone about these two eyepieces is to try before you buy if at all possible and do not jump to any conclusions based on one persons performance in a telescope that is different to your own

Cheers
John B

[ausastronomer (John Bambury)]

Originally Posted by Rodstar

Hi John, thanks for your careful analysis of my EP situation. I am aware of the various issues you raise, and have contemplated enlarging my Ethoi collection. Alas, I would prefer to spend my money on other things at this stage.

My interest in the Delos is not driven by what other EPs I may have in a similar focal length or TFOV, but rather the more intangible notion of "comfort". Part of this may be eye relief, but there can be other more subjective issues at play.

I adored my 22mm Panoptic and regret selling it. Notwithstanding its slightly inferior performance at edge of field, and narrower field of view (68 degrees) it was, for reasons which are perhaps a little hard to pin down, the most comfortable EP I have ever had. When I had it, it spent more time in the focuser of the Mary Rose than any other EP.

With my current line up, the 20mm Nagler plus Paracorr is my default observing choice. This renders an effective focal length of 17mm. While I love the 20mm Nagler, it does have fairly tight eye relief, which means that it is not optimally comfortable, and when glasses wearers share the views with me through the Mary Rose, it is definitely far from ideal for them.

I confirm that the 13 Ethos is not useful more often than not. The seeing in my area does not support 200x all that often. Having something in the 17mm area is a logical slot for me for times when the seeing is just not quite up to scratch for the 13E.

I am interested to know how the 17.3mm Delos may perform as an alternative. It might just be near dang perfect, for a pretty reasonable price that even SWMBO (aka the Minister for Finance) cannot argue with.

I am particularly interested to know how it performs without a Paracorr. If coma is an issue, then I will not be purchasing one.

Hi Rod,

I understand exactly where you are coming from and figured seeing issues was the likely problem with your 13mm ETHOS.

I am interested to know how the 17.3mm Delos may perform as an alternative. It might just be near dang perfect, for a pretty reasonable price that even SWMBO (aka the Minister for Finance) cannot argue with.

It might not be also. Read on

I know you had issues using my Pentax XW's with regard to eye placement and blackouts. This is a problem experienced by about 10% of users who don't wear eye glasses with the Pentax XW's, due to the long eye relief of the eyepiece and the fact that the eye guard when adjusted for an eye glass wearer is automatically then not properly adjusted for a non eye glass wearer.

I have read several reports on Cloudy Nights from people who have had both the 10mm Pentax XW and the 10mm Delos. Looking at the opinions which I believe were objective, some people have decided to keep the 10mm Delos while others have gone with the 10mm Pentax based on the fact their performance was equal, but the 10mm Pentax XW was easier to use and hold the exit pupil than the DELOS. Based on your past experience with the Pentax XW's and the user feedback, you "may" find the DELOS difficult to use compared to other eyepieces having slightly shorter eye relief.

I can only suggest you try before you buy, if at all possible.

Cheers,
John B

[Fox]

Thanks John, I thought my comments would 'stir the pot' and you might chime and set the record straight about curvature and the XW's. I certainly love my Pentax XW 7mm, and I wish the 14mm had shown the same performance in my scope (to my eyes). I would add that I still went for the 7mm XW, after I had tried and sold on the 14mm XW; the 7mm will never leave my side!

[bobson (Bob)]

Hmm...

Don't lose sight of the fact that Americans are a very patriotic race and very loyal to their own brands and a lot of those reports are not going to be as objective as they might be.

Yes, probably as objective as you John can be when you say:

I haven't used the DELOS yet

But will give "objective" review about DELOS.

I haven't used the DELOS yet but I have used the ETHOS countless times in a number of different focal lengths and in none of those focal lengths does the ETHOS outperform the equivalent focal length Pentax XW in terms of light throughput, contrast and sharpness. Their performance is extremely close, but if I had to split them, I would lean very slightly to the Pentax XW's. That is academic because I prefer more eye relief than what the ETHOS offers. I read countless internet reports on US forums about how this ETHOS and that ETHOS outperformed its Pentax XW equivalent, on such and such a target. That is just plain poppycock.

You are right, considering what you based your objectiveness on what you wrote is as much plain poppycock as you said it yourself.

The best and most objective advice you gave is this one though:

The best advice I can give anyone about these two eyepieces is to try before you buy if at all possible and do not jump to any conclusions based on one persons performance in a telescope that is different to your own

cheers

[ausastronomer (John Bambury)]

Congratulations Bob,

It is replies like yours which make me question why I waste my valuable time posting replies to people on this forum trying to help them, when thrown into the mix I have to [moderated]

Cheers,
John B

[Profiler (Profiler)]

John

I for one can assure you that the time you provide in sharing your advice, input, experience and obvious sagacity in critically considering such issues is very much and gratefully appreciated.

The independent testimony to the merits and worth of your contributions to these forums is routinely demonstrated by the repeated and numerous requests different members make actively seeking your specific views.

[Rodstar (Rod)]

Originally Posted by ausastronomer

I can only suggest you try before you buy, if at all possible.

Cheers,
John B

Anyone likely to come to the Central Coast group (Mangrove Mountain) in the next few months with a 17.3mm Delos??

[davewaldo]

Hi John, although I haven't been posting in a lot of the threads you have been giving advice in, I have been very glad you took the time. I'm also rethinking my EP collection and some of the recent threads have been very valuable. Thanks mate!

Cheers!

[bobson (Bob)]

{moderated}.

Is this how you deal with criticism? You and your rat face follower are always here to put down anyone who dares to say anything against Pentax XW eyepieces. You gave your "objective" review and concluded how DELOS is not as good as Pentax eyepieces even though you admit never looked through one!

Need I say more?

I appreciate your and anyone else input but only when its based on facts and your own experience using them. You wrote numerous reviews about eyepieces you have or used. And like I said everyone appreciate and thank you for it. But when you write about something based on assumption and want us to believe in it then I feel I should question that weather you and alike like it or not. You know about DELOS as much as you said yourself that can fit on postage stamp!

cheers