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Has Tele Vue Forsaken Long Focal Lengths?

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#1 Jeff Morgan

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Posted 28 January 2013 - 02:15 PM

Some of you may recall a recent thread on this forum 22 pan vs 22t4. Once again it made me aware that I need to evaluate what I am using in that focal range. Currently, it is the venerable 22 Panoptic. It is superb in the longer focal ratio scopes I prefer. But my rational brain realizes I should acquire a 22 Nagler T4 for comparison, especially in light of how much I loved the 17T4.

I finally realized the root of my procrastination - the feeling that Tele Vue may be close to offering something substantially better in that range. After Delos there was speculation on a "Panoptic Makeover". Or perhaps even lighter Naglers (such as the revised 20mm model). But is that justified? I offer this timeline, based on product announcements in Tele Vue ads from Sky & Telescope:

- 22mm Nagler Type 4, June 1999;
- 31mm Nagler Type 5, December 1999;
- 26mm Nagler Type 5, October 2002;
- 24mm Panoptic, February 2003; and
- 41mm Panoptic, June 2003.

For the last ten years, Tele Vue has introduced nothing longer than 22mm. Most of their work has been in the short (and very short) focal lengths.

Could one imply that we are "due" to see some introductions in the longer lengths, or has Tele Vue lost interest?

#2 BillP

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Posted 28 January 2013 - 02:37 PM

Frankly, I don't think they have the interest. They can always argue that they have existing, excellent eyepieces in long focal lengths. 55 Plossl, 41/35 Pan, 31/26 Naglers, so why need more?

I of course agree with you. When new designs come out using latest glasses and coatings and production techniques, I feel that these new lines should as standard fare offer a 1.25" and 2" focal length that maximizes the barrel size. Neither the Ethos or the Delos do this and frankly, IMO it is a shame. Of course there may be the argument that the particular design is not practical to get to those longest focal lengths. To that I counter then offer a different design with the same optical parameters of ER and AFOV that does reach the max TFOV and brand it the same -- so give us a 72 degree Delos in 23mm or so and a 100 degree Ethos in 25mm or so. Don't care that the optical design might depart from the others as long as the AFOV, ER, and level of correction is maintained. This way we can build our eyepiece stalls with consistency. I know I was very happy when TV came out with the Delos line, then got bumbed when I would have to get a 24 pan to max my 1/25" capabilitiy. Don't want to do that and have a context switch like that...so not a candidate line of EPs for me.

#3 Grava T

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Posted 28 January 2013 - 03:54 PM

I think most, if not all, Televue eyepieces are designed to be used with their own refractors or at least short focal length newtonians. Medium to high power eyepieces are more useful I would imagine. Hard to improve on the low power choices already offered by TV.

#4 Jon Isaacs

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Posted 28 January 2013 - 04:13 PM

I think most, if not all, Televue eyepieces are designed to be used with their own refractors or at least short focal length newtonians. Medium to high power eyepieces are more useful I would imagine. Hard to improve on the low power choices already offered by TV.


:waytogo:

Personally I am fine the existing eyepieces. I have a set of eyepieces from TeleVue that do the job. The 31mm Nagler is a fine eyepiece. To me, new and different are new objects in the sky to observe, new sites to observe from. A trip 5 hours down the road to the Baja Dark Skies Inn is going to make far more difference in what I see than a new eyepiece or two.

Jon

#5 BillP

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Posted 28 January 2013 - 04:34 PM

I think most, if not all, Televue eyepieces are designed to be used with their own refractors or at least short focal length newtonians. Medium to high power eyepieces are more useful I would imagine. Hard to improve on the low power choices already offered by TV.


Hmmm... :mrevil:

1. Is the 24mm Panoptic improvable (as TV's max TFOV 1.25" wide field eyepiece)? I would say easily yes! Eye relief is way too short on this eyepiece. Needs to be 20mm. So there's a much needed improvement.

2. 41Pan/31T5 - Are these both entirely "perfect"? Nope. First off...they are massive and heavy. Improvements can be to lighten them and decrease their physical size. Plus, I need a 2" 100 degree eyepiece that gives widest TFOV capable with a 2" barrel. So not necessarily an improvement of these as much of a missing eyepiece.

Always room for improvement.

#6 turtle86

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Posted 28 January 2013 - 04:57 PM

I really would've liked a 25mm Ethos but I'm pretty happy with the 31mm Nagler. It sure seemed stupid big when I first got it but I've since gotten used to its size and weight. I've definitely gotten accustomed to its great wide field views. :grin:

#7 Jon Isaacs

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Posted 28 January 2013 - 04:58 PM

Plus, I need a 2" 100 degree eyepiece that gives widest TFOV capable with a 2" barrel. So not necessarily an improvement of these as much of a missing eyepiece



I am OK with 82 degree eyepieces. ES filled in the 25mm 100 degree. I am not sure there is room in the barrel for TeleVue to build an eyepiece 100 degree 25mm of sufficient quality to please Uncle Al. The 31mm Nagler uses all of a 2 inch barrel but only has an effective field stop diameter of 42mm.

In any event, I don't "need" any eyepieces but they are fun to have.

Jon

#8 BillP

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Posted 28 January 2013 - 05:12 PM

I am not sure there is room in the barrel for TeleVue to build an eyepiece 100 degree 25mm of sufficient quality to please Uncle Al.


I have heard that expressed before. However, another way of saying that is "I can't make a 25mm 100 degree eyepiece of sufficient quality." If they really can't make it then should they be considered a leader in the industry? Can't have it both ways...I'm a leader and I can't do stuff so let other innovate...but I'm the leader, etc. Contradictory.

#9 tomcody

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Posted 28 January 2013 - 05:26 PM



1. Is the 24mm Panoptic improvable (as TV's max TFOV 1.25" wide field eyepiece)? I would say easily yes! Eye relief is way too short on this eyepiece. Needs to be 20mm. So there's a much needed improvement.
[/quote]
That's only your opinion, I find 15mm eye relief to be Perfect! If you want 20mm? buy a Delos.
Rex

#10 Mike W

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Posted 28 January 2013 - 05:34 PM

I agree on the eye relief ( there's worse offenders for sure) but I don't wonder if increasing the eye relief wouldn't also increase the size. As a favorite for binoviewers as they are, they might shoot themselves in the foot.

I think most, if not all, Televue eyepieces are designed to be used with their own refractors or at least short focal length newtonians. Medium to high power eyepieces are more useful I would imagine. Hard to improve on the low power choices already offered by TV.


Hmmm... :mrevil:

1. Is the 24mm Panoptic improvable (as TV's max TFOV 1.25" wide field eyepiece)? I would say easily yes! Eye relief is way too short on this eyepiece. Needs to be 20mm. So there's a much needed improvement.

2. 41Pan/31T5 - Are these both entirely "perfect"? Nope. First off...they are massive and heavy. Improvements can be to lighten them and decrease their physical size. Plus, I need a 2" 100 degree eyepiece that gives widest TFOV capable with a 2" barrel. So not necessarily an improvement of these as much of a missing eyepiece.

Always room for improvement.



#11 rockethead26

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Posted 28 January 2013 - 05:40 PM

[quote name="tomcody"]

1. Is the 24mm Panoptic improvable (as TV's max TFOV 1.25" wide field eyepiece)? I would say easily yes! Eye relief is way too short on this eyepiece. Needs to be 20mm. So there's a much needed improvement.
[/quote]
That's only your opinion, I find 15mm eye relief to be Perfect! If you want 20mm? buy a Delos.
Rex [/quote]

Uh, they don't make a 24mm Delos. I think that's the point.

#12 tomcody

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Posted 28 January 2013 - 05:45 PM

[quote name="rockethead26"][quote]

1. Is the 24mm Panoptic improvable (as TV's max TFOV 1.25" wide field eyepiece)? I would say easily yes! Eye relief is way too short on this eyepiece. Needs to be 20mm. So there's a much needed improvement.
[/quote]
That's only your opinion, I find 15mm eye relief to be Perfect! If you want 20mm? buy a Delos.
Rex [/quote]

Uh, they don't make a 24mm Delos. I think that's the point. [/quote]
And they don't make a 24 Panoptic with 20mm of eye relief. It would make more sense to suggest a 24mm Delos , a line with constant 20mm eye relief than to change a proven design with a good following. That's the point.
Rex

#13 sniperpride

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Posted 28 January 2013 - 06:43 PM

Except that they dont intend to make a Delos at longer focal lengths.
The point of this was to upgrade current existing focal lengths. Panoptics, long FL naglers.

#14 Starman1

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Posted 28 January 2013 - 06:59 PM

Frankly, I don't think they have the interest. They can always argue that they have existing, excellent eyepieces in long focal lengths. 55 Plossl, 41/35 Pan, 31/26 Naglers, so why need more?

I of course agree with you. When new designs come out using latest glasses and coatings and production techniques, I feel that these new lines should as standard fare offer a 1.25" and 2" focal length that maximizes the barrel size. Neither the Ethos or the Delos do this and frankly, IMO it is a shame. Of course there may be the argument that the particular design is not practical to get to those longest focal lengths. To that I counter then offer a different design with the same optical parameters of ER and AFOV that does reach the max TFOV and brand it the same -- so give us a 72 degree Delos in 23mm or so and a 100 degree Ethos in 25mm or so. Don't care that the optical design might depart from the others as long as the AFOV, ER, and level of correction is maintained. This way we can build our eyepiece stalls with consistency. I know I was very happy when TV came out with the Delos line, then got bummed when I would have to get a 24 pan to max my 1/25" capabilitiy. Don't want to do that and have a context switch like that...so not a candidate line of EPs for me.

1) The Panoptic line (41/35/27/24/19) complements the Delos (17.3/14/12/10/8/6/4.5/3.5), so why should TV come out with longer Delos?
2) A Delos 23 would be 2" or have vignetting issues.
3) A 25 Ethos (not changing the internal design) would have poorer edge correction and significant vignetting, which TV won't do, not to mention being ridiculously expensive if the same glass types were used (not to mention weight). ES made a lot of compromises to introduce the 25 (it doesn't have the same internal design as the 20/14/9), and the market may say those compromises were justified and OK, but TeleVue has already said they won't. So you won't see a 25 Ethos.
4) Likewise, the Nagler line is fairly complete. Mix T5s and T6s, and you have: 31/26/20/16/13/11/9/7/5/3.5/2.5 which really kind of covers it.

With positive/negative eyepiece designs now dominating the market in wide and ultrawide fields, you have to look at how an eyepiece would maximize the field stop for the barrel diameter. Would a 1.25" 23mm Delos be practical if it had to be, say, several ounces heavier and a couple inches larger in diameter and maybe a lot more expensive? Then everyone would say, "I don't see why anyone would get this when a 21 Ethos has a wider true field and weighs less......"
Sometimes the largest practical field stop for a given diameter is smaller than the inside diameter of the barrel. Even Pentax went with 2" for 30 and 40mm XWs. The 31mm Nagler has a 42mm field stop when the inside diameter of the barrel is at least 46.5mm. Would you contemplate buying a 31mm eyepiece a pound heavier and 2" larger in diameter just to get a slightly larger field stop? Or an eyepiece with vignetting and poorer edge correction to keep the size the same but expand the field stop?

Probably not. And neither would I if I knew that compromise had been made.

I could see some company, and it probably would be TeleVue, coming out with a line of long eye relief 82 degree eyepieces. That would heavily expand the market for 82 degree eyepieces, whether they had field stops of the I.D. of the barrels or not.

#15 Paul G

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Posted 28 January 2013 - 07:52 PM

[quote name="tomcody"]

1. Is the 24mm Panoptic improvable (as TV's max TFOV 1.25" wide field eyepiece)? I would say easily yes! Eye relief is way too short on this eyepiece. Needs to be 20mm. So there's a much needed improvement.
[/quote]
That's only your opinion, I find 15mm eye relief to be Perfect!
Rex [/quote]

:bow: I also find it very comfortable, no need for more eye relief, particularly if that means the eyepiece would be physically larger.

#16 Grava T

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Posted 28 January 2013 - 08:19 PM

I think most, if not all, Televue eyepieces are designed to be used with their own refractors or at least short focal length newtonians. Medium to high power eyepieces are more useful I would imagine. Hard to improve on the low power choices already offered by TV.


Hmmm... :mrevil:

1. Is the 24mm Panoptic improvable (as TV's max TFOV 1.25" wide field eyepiece)? I would say easily yes! Eye relief is way too short on this eyepiece. Needs to be 20mm. So there's a much needed improvement.

2. 41Pan/31T5 - Are these both entirely "perfect"? Nope. First off...they are massive and heavy. Improvements can be to lighten them and decrease their physical size. Plus, I need a 2" 100 degree eyepiece that gives widest TFOV capable with a 2" barrel. So not necessarily an improvement of these as much of a missing eyepiece.

Always room for improvement.


Point taken and I guess there is always room for improvement but it's like re-recording "Stairway to Heaven" to make it better. Why would you want to? :)

#17 johnnyha

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Posted 28 January 2013 - 09:48 PM

I have heard that expressed before. However, another way of saying that is "I can't make a 25mm 100 degree eyepiece of sufficient quality." If they really can't make it then should they be considered a leader in the industry? Can't have it both ways...I'm a leader and I can't do stuff so let other innovate...but I'm the leader, etc. Contradictory.


I think you might be confusing quality with quantity Bill. ;) The decision to NOT make the 25E is what makes Nagler an industry leader. The 21 Ethos was an innovation, the 25 ES 100 is a knockoff that makes compromises as Don has pointed out, compromises that TV is unwilling to make.

#18 John F

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Posted 28 January 2013 - 10:51 PM

Jeff,

I've owned both the 22mm Pan and T4 Nagler in the past. Yes, the T4 has a larger and somewhat more immersive field than the Pan does. However, it weighs 8 ounces more and has that click-stop eyeguard which some observers don't like.

The Pan on the other hand still has a fairly large TFOV and AFOV, 15mm of eye relief, and is not too large or heavy. And all around, it is one of the most relaxing to observe with eyepieces that I've ever used.

If you already have one, and have been very pleased with it, count yourself fortunate and just keep using it. If you get the 22mm T4 then you may start having doubts about whether you should have got 21mm Ethos instead.

John Finnan

#19 faackanders2

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Posted 28 January 2013 - 11:20 PM

I have heard that expressed before. However, another way of saying that is "I can't make a 25mm 100 degree eyepiece of sufficient quality." If they really can't make it then should they be considered a leader in the industry? Can't have it both ways...I'm a leader and I can't do stuff so let other innovate...but I'm the leader, etc. Contradictory.


I think you might be confusing quality with quantity Bill. ;) The decision to NOT make the 25E is what makes Nagler an industry leader. The 21 Ethos was an innovation, the 25 ES 100 is a knockoff that makes compromises as Don has pointed out, compromises that TV is unwilling to make.


Industry leaders innovate and push the envelope (like TV did when they created the first Ethos). Sometimes compromizes have to be accepted (like Nagler zooms don't have 82 AFOV).

#20 Starman1

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Posted 29 January 2013 - 12:08 AM

Nearly every eyepiece has compromises of some sort, at least in one or more design parameters.
There is no such thing as a perfect eyepiece, both in terms of personal preferences (eye relief, apparent field), design (weight, size, complexity of manufacture), and optical parameters (amount of AMD, RD, astigmatism, lateral color, transmission, etc.).
I've been doing this a while (50 years this year), and I've never seen the perfect eyepiece. And if some company made it, it would be too expensive for any of us to afford it anyway.
So we deal with eyepieces that have imperfections; some imposed by the imperfect viewing device (the eye) and others by the laws of optics (the inability to solve for both zero AMD and zero RD at the same time), and still others the marketplace (price, weight, size).

I last worked on the Eyepiece Buyer's Guide in 2009 and there were nearly 1600 different eyepieces available from 2mm to 56mm (and a few specialty eyepieces even longer), and I've started the process of re-doing it for 2013 and along the way I'm discovering a lot of companies have disappeared. Very few companies have expanded their lines.

I hope TeleVue continues to innovate. I hope that many Chinese companies successfully market their wares. There are a few up-and-comers. I'm not sure we ever needed the plethora of offerings that were around in 2009, but I don't want to see too major a drop in the number of choices, either. We all benefit from innovation and competition. State of the Art will always cost more, and it will never be for everyone. But with larger production comes lower costs and more sales, so perhaps we could deal with a few less players and fewer choices. Then, perhaps, our favorite companies might make a profit and keep innovating.

#21 Jeff Morgan

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Posted 29 January 2013 - 02:23 AM

I think most, if not all, Televue eyepieces are designed to be used with their own refractors or at least short focal length newtonians. Medium to high power eyepieces are more useful I would imagine. Hard to improve on the low power choices already offered by TV.


When I started the thread, I knew there would be no "answers", but was hopeful of a robust discussion and it has happened.

Not to be argumentative, put a few points stand out:

- As the old saying goes, "you don't know what you don't know". While it may be hard to imagine improvements in the longer focal length offerings, Tele Vue has a rather pronounced capability to surprise us. Before the first Nagler design, who could have guessed it could be that good?

- Many (some :grin:) thought the Radian line could not be improved. Now we have Delos.

- Granted that for the most part long focal length eyepieces already have good eye relief, but even a simple weight reduction is a huge improvement for the owners of small scopes (like Tele Vue refractors) and even the medium ones (case study: 20mm Nagler Type 2 to Type 5). Perhaps another area for improvement would be Pincushion, one of the frequent knocks against the Panoptic line.

- There has been some who suggest the low power/long focal lengths are not so important for the faster focal ratio scopes of today. I would say that Tele Vue historically has been a player in the fast refractor market. At f/5 one still can productively use a 35mm eyepiece. Indeed, Al Nagler says that for refractors there is no effective upper limit on exit pupil. And f/5 is perhaps the most common focal ratio for reflectors too.

- I was wondering if I missed something in the timeline, and it appears no one caught an error. Point being, ten years is an exceptionally long period of time for a designer in the prime of his life to be absent from an important market segment. Granted Al Nagler has provided for the continuity of the company, but ten years is still a long time from a company perspective too.

#22 Jon Isaacs

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Posted 29 January 2013 - 07:39 AM

- There has been some who suggest the low power/long focal lengths are not so important for the faster focal ratio scopes of today. I would say that Tele Vue historically has been a player in the fast refractor market. At f/5 one still can productively use a 35mm eyepiece. Indeed, Al Nagler says that for refractors there is no effective upper limit on exit pupil. And f/5 is perhaps the most common focal ratio for reflectors too.



Consider this:

The 31mmm Nagler, the 35mm and 41mm Panoptics are good enough that the edge corrections issues are not the eyepiece but rather the telescope. The center sharpness issues are not the limitations of the eyepiece but rather the resolution of the observer's eye.

If you want that perfect sharp edge in a refractor, particularly around F/5, the eyepiece is not the problem, it's the telescope. Uncle Al has this one covered nicely, start with a NP-101 or NP-127, add the 31mm Nagler and it's about as close to heaven as we mortals will ever get.

The 42mm field stop of the 31mm Nagler means the best case scenario is an increase of 10% TFoV, not a lot.. If that last 10% is desired, there is the 41mm Panoptic.

Jon

#23 BillP

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Posted 29 January 2013 - 09:52 AM

[quote name="tomcody"]

1. Is the 24mm Panoptic improvable (as TV's max TFOV 1.25" wide field eyepiece)? I would say easily yes! Eye relief is way too short on this eyepiece. Needs to be 20mm. So there's a much needed improvement.
[/quote]
That's only your opinion, I find 15mm eye relief to be Perfect! If you want 20mm? buy a Delos.
Rex [/quote]

I disagree. There are many many posts of eyeglass wearers who feel the 24Pan is not quite sufficient and needs extended eye relief to be practical for them. So it very ddefinitely needs to be improved. Also, Tele Vue has no other offering of a 1.25" wide-field eyepiece which maximizes the TFOV capable from the barrel and also has eye relief sufficient for eyeglass wearers. The 24 Pan and 32 Plossl are their only two offerings that maximize the TFOV potential of the 1.25" barrel. Since the 32 Plossl is not a wide-field this leaves only the 24 Pan. The Delos is not an option since they offer no 1.25" Delos that maximizes the TFOV potential of the barrel.

#24 BillP

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Posted 29 January 2013 - 09:54 AM

...the 25 ES 100 is a knockoff that makes compromises as Don has pointed out, compromises that TV is unwilling to make.


What other 25mm 100 degree design is it knocking off?? The ES offering is an innovation for the consumer. One can't claim "knockoff" unless one has privy to the optical designs of both...which no one here has. FYI, all designs have compromises, including Tele Vue designs. It would not be logical to say that TV's compromises in a design are somehow not compromises and only compromises of other vendor are.

If the "issue" is that Tele Vue can't use their current Ethos design to get a good image at a 25mm Focal length, then the solution is not to throw up one's hands and say it can't be done...instead the solution is to create the design which can achieve 25mm at 100 degrees to their satisfaction. Many consumers obviously desire a 100 degree eyepiece which maximizes the TFOV capability of a 2" barrel. IMO, one can't claim "unwilling to compromise" as a reason. The real intent I am sure is that they are unwilling to utilize the Ethos design for a 25mm 100 degree eyepiece because the design can't maintain optical performance goals of the Ethos series. This is the more accurate statement and far from a statement saying it is not feasible. The solution for TV if the Ethos design can't handle 25mm acceptably is to create a new 100 degree design to handle the 25mm and longer focal lengths...so keeping with their past naming would be an Ethos Type-2.

#25 turtle86

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Posted 29 January 2013 - 10:13 AM

A 25 Ethos (not changing the internal design) would have poorer edge correction and significant vignetting, which TV won't do, not to mention being ridiculously expensive if the same glass types were used (not to mention weight). ES made a lot of compromises to introduce the 25 (it doesn't have the same internal design as the 20/14/9), and the market may say those compromises were justified and OK, but TeleVue has already said they won't. So you won't see a 25 Ethos.



This has me curious as to how well the ES 100 25mm performs in comparison to the other ES 100 eyepieces. :question:

A 25mm Ethos would've been nice, but only if Televue had been able to maintain the image quality of the 21mm Ethos and 31mm Nagler. For my purposes, not really much point in springing for a 25mm Ethos if the image quality wouldn't have been as good as the 31mm Nagler. Sure, all eyepiece designs involve compromises, the tricky part is where to draw the line...






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