Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
Get a Cloudy Nights T-Shirt Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green GuÖ uh, User

Equipment Discussions >> Eyepieces

Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | (show all)
94bamf
Carpal Tunnel
*****

Reged: 12/15/08

Loc: Kansas City,Mo
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: tmbuser6]
      #5047101 - 01/31/12 12:16 AM

Quote:

Quote:

There are quite a few 2" EPs over 21mm. I have a TeleVue 35mm Panoptic. I have 42mm and 50mm 2" EPs ordered and on the way now.




Mr. Black, et al., I think the matter is a bit more complicated than you may realize. You see, it is already well established that the ES-100 design is at least /very/ similar to that of the Ethos, at least according to x-ray analysis. Basically, these eyepieces work with a negative-power Smyth lens group /ahead/ of the field stop, which is internal, about half way to the next lens, which is a positive meniscus. These 4 lenses operate together as a powermate-like group with the field stop placed within the group after the third lens.

Look at the bottom of any of these eyepieces and you will see that there is no external field stop present like in a normal eyepiece, and if you bring your finger up to the field lens while looking through, you will not find any point where you can bring your finger into focus looking thorough the eyepiece! That is because the focal plane is well inside.

It is this group which is both essential to and really the basis for the performance of the eyepiece. Due to the negative power of the Smyth lens group and the placement of the focal plane and field stop inside where they must be, the aperture of the Smyth group must be /larger/ than the field stop aperture. If you look hard into the bottom of one of these eyepieces, you may be able to tell that.

The net result of all of this is that this places an upper limit to the maximum focal length of such an eyepiece to be around 22mm if you wish to not have any vignetting. So, unless Explore has reinvented optics (I don't expect that to be the case), the only other option I can see is to allow for some vignetting to take place.

There were a great many people hoping for a 100 degree Ethos from TeleVue that was long enough to take the place of the 31mm Nagler so that they could retire that eyepiece in favor of an all-Ethos line of eyepieces, and they were hoping for something like a 24-25mm for that purpose, but the practical limit of the design without making compromises was 21mm due to the confines of a 2" barrel, that is why they didn't make it any longer. In order to make a longer focal length, you would need to go to a larger barrel.

And I suspect that was a similar constraint in ES choosing 20mm for their very similar eyepiece. SO, either Explore has chosen to allow a considerable amount of vignetting to occur in the periphery, or they have departed greatly from the original design, which I do not see happening while also maintaining equal performance. Therefore, we do not really know what we are buying here and I myself would be a bit hesitant to invest in one blindly before others have had a chance to sample the eyepiece and evaluate it.

The one maxim that holds true for all of optics is that there are no free lunches: You do not gain in one area without giving something up somewhere else. For ES to have crossed the 22mm threshold still within the limits of a 2-inch barrel, they must have made some compromises elsewhere. ;^)

I would expect the eyepiece to likely have both visible vignetting (limb-darkening around the edges), not be a true 100-degree AFOV, and/or probably have a loss of eye relief (smaller eye lens) as a consequence, which is already at a minimum in the present ES design.

Regards,

Wayne




Good stuff..

I think we are at an interesting point for Explore Scientific. It seems pretty well established that their other 100 deg AFOV eyepieces are pretty close to copies/clones of the TV Ethos line, whether people want to believe it or not(or care). It also seems well established that their clones/copies don't quite fully meet the quality/correction/execution of the Ethos line. This is what makes the 9mm 120 deg AFOV and the 25mm 100 deg AFOV eyepieces quite interesting. Two different focal length/AFOV combos that Televue has never produced. It really is a test to see if ES can match the quality/correction/execution of their other "copied" 100 deg AFOV eyepieces(20mm,14mm,9mm). I wish them well, and I hope they can do it. If either or both eyepieces have "issues" like vignetting or poor outer field correction, or other aberrations, it could hurt..

Ken


Post Extras: Print Post   Remind Me!   Notify Moderator  
Ernest_SPB
sage


Reged: 11/13/10

Loc: St.-Petersburg, Russia
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: 94bamf]
      #5047182 - 01/31/12 01:38 AM

I thought before that only reason for TV do not produce 25 mm Ethos is prevention of internal concurrence with their flagship 31 mm Nagler.

It looks like ES is free from the reason and does not afraid concurrence too much.


Post Extras: Print Post   Remind Me!   Notify Moderator  
tmbuser6
sage
*****

Reged: 07/01/11

Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: 94bamf]
      #5047233 - 01/31/12 02:53 AM

Quote:

Good stuff..

I think we are at an interesting point for Explore Scientific. It seems pretty well established that their other 100 deg AFOV eyepieces are pretty close to copies/clones of the TV Ethos line, whether people want to believe it or not(or care). It also seems well established that their clones/copies don't quite fully meet the quality/correction/execution of the Ethos line. This is what makes the 9mm 120 deg AFOV and the 25mm 100 deg AFOV eyepieces quite interesting. Two different focal length/AFOV combos that Televue has never produced. It really is a test to see if ES can match the quality/correction/execution of their other "copied" 100 deg AFOV eyepieces(20mm,14mm,9mm). I wish them well, and I hope they can do it. If either or both eyepieces have "issues" like vignetting or poor outer field correction, or other aberrations, it could hurt..

Ken




Ken, both the ES-100 and Ethos have been x-rayed and look too close (identical really) to be a coincidence. The Ethos has been taken apart and analyzed by people I know. Both the Ethos and the ES-100 have been rigorously tested side by side, and there is no doubt to me and others that the ES-100 is very good for the money, and very close, but the extra price of the Ethos buys you better optical quality which diverges apart more greatly the further off axis you go, and without the essential eye relief the Ethos has which makes it comfortable to use. THAT is what you are buying with the Ethos and giving up with the Explore. Not that the Explore isn't a good value, but surely no one thinks they are getting as good a design at hundreds of dollars less? Televue are the grandfathers of such designs and would not charge so much at their own peril of lost sales without good reason if they didn't have to.

When the 21mm Ethos came out, it came out under 22mm AS PREDICTED. The Ethos SX design at 110 degrees is just beyond the eye's range to see all at once. I see the 9mm 120 degree design as ponderously heavy and essentially pointless as no one will ever be able to see the entire FOV at once, so they are really paying for something they can never use. In practice, the view will never look any wider than an SX. In my opinion they are playing a numbers and marketing game with people. I've used hundreds of eyepieces over 46 years, I have yet to have any of them fog up for not being purged or sealed with o-rings. But if you had such a sealed eyepiece, you sure would be hesitant to take it apart, wouldn't you?

I think your assessments above are indeed quite accurate, and it will be interesting to read from those who plunk down $1000 and $500 on two really unknown and untested designs from a company which has, to date, seemingly built most of its laurels on the work of others, making less expensive copies. If we were talking about small sums of money I could understand it, but now we are talking about people pre-ordering a ONE-THOUSAND DOLLAR eyepiece that no one has ever even seen yet? And a $500 25mm eyepiece that TeleVue themselves would not build? Yes, expect to pay about $500 for it.

Frankly, it amazes me that when the 13mm Ethos came out in the fall 2008, most people were denouncing them as a gimmick, unnecessary and vastly too large, heavy and expensive; now folks are racing to enthusiastically buy a $1000 3 pound eyepiece with twelve lenses in it. That is like stacking an Abbe Ortho on top of another Abbe Ortho on top of another. But if anyone did that, they would be considered crazy, not revolutionary ;^)

The idea of a 7 or 8 element eyepiece has been around for a long time, but a 12-element design? That is a telephoto camera lens! That is four-fold the complexity of an 8-element design. Do you think there will be some ghosting issues and other losses there? ;^)

What are people really buying with these garish designs, good optics or merely an idea and a status symbol to hang on their telescopes? Something to think about before you mortgage the house. The greatest truth in optics is that there are no free lunches. You ALWAYS give something up to gain something somewhere else.

Regards,

Wayne


Post Extras: Print Post   Remind Me!   Notify Moderator  
rockethead26
Post Laureate
*****

Reged: 10/21/09

Loc: Arizona, USA
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: tmbuser6]
      #5047380 - 01/31/12 07:43 AM

Quote:

I've used hundreds of eyepieces over 46 years, I have yet to have any of them fog up for not being purged or sealed with o-rings.




But, as reported here on CN, others have.

Quote:

But if you had such a sealed eyepiece, you sure would be hesitant to take it apart, wouldn't you?




So ES decided to purge their EPs only so no one would take them apart and look at the construction?

Quote:

Frankly, it amazes me that when the 13mm Ethos came out in the fall 2008, most people were denouncing them as a gimmick, unnecessary and vastly too large, heavy and expensive; now folks are racing to enthusiastically buy a $1000 3 pound eyepiece with twelve lenses in it. That is like stacking an Abbe Ortho on top of another Abbe Ortho on top of another. But if anyone did that, they would be considered crazy, not revolutionary ;^)




And, history repeats itself yet again.

Quote:

The idea of a 7 or 8 element eyepiece has been around for a long time, but a 12-element design? That is a telephoto camera lens! That is four-fold the complexity of an 8-element design. Do you think there will be some ghosting issues and other losses there? ;^)

What are people really buying with these garish designs, good optics or merely an idea and a status symbol to hang on their telescopes? Something to think about before you mortgage the house. The greatest truth in optics is that there are no free lunches. You ALWAYS give something up to gain something somewhere else.

Regards,

Wayne




Sound like what folks were saying when the 7-8 element EPs were first introduced. Nothing ever changes except change itself.

It will certainly be interesting to get some first-hand reports of the 25mm 100į and the 5.5mm 100į, not to mention the 120į 9mm.

With the ES company history of producing some really excellent eyepieces and refractors for a very fair price, I really don't think ES would introduce 3 new poorly designed EPs that would wreck their growing reputation just to out-do the competition.

Just my two cents.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Darenwh
Carpal Tunnel


Reged: 05/11/06

Loc: Covington, GA
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: Scott in NC]
      #5047492 - 01/31/12 09:17 AM

Quote:

Quote:

Actually the 5.5mm will be out close enough to my wife's birthday that I could buy it for her!!




Hope she's an astronomer, too. Otherwise you'll really be in the doghouse!



It's my hobby but she likes going out with me. Still, I will be in the dog house but a few days in the dog house is a small price to pay for such grand views...


Post Extras: Print Post   Remind Me!   Notify Moderator  
Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Scotophobe Maryland, USA
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: Darenwh]
      #5047513 - 01/31/12 09:32 AM

As long as you have a good view of the sky from the dog house, I don't see a problem.


Mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
Darenwh
Carpal Tunnel


Reged: 05/11/06

Loc: Covington, GA
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: rockethead26]
      #5047561 - 01/31/12 10:05 AM

Quote:

Quote:

Frankly, it amazes me that when the 13mm Ethos came out in the fall 2008, most people were denouncing them as a gimmick, unnecessary and vastly too large, heavy and expensive; now folks are racing to enthusiastically buy a $1000 3 pound eyepiece with twelve lenses in it. That is like stacking an Abbe Ortho on top of another Abbe Ortho on top of another. But if anyone did that, they would be considered crazy, not revolutionary ;^)




And, history repeats itself yet again.






I see the way people thought of the Ethos in this manner as being a reaction to it's size more than anything else. Many people considered it to be crazy due to the size and balance issues it would cause. Since then people have learned to deal with balance issues well enough that they are less inclined to consider a large eyepiece to be crazy. Now, we have become believers in the wider AFOV eyepieces.

Per Wiki the eye can see in each direction at least 60 degrees so 120 degree eyepieces should be fine for the eye. I would love to try one of those eyepieces but they are out of my budget range. I suspect, with Explore Scientific's record, that these will be very nice eyepieces.

Will there be vignetting in the outer regions of the FOV? Perhaps but if it's not too intrusive I think many people will be quite satisfied anyways.

Can the eye see details in the entire field of view? Quite likely not but they will be able to see detail in as much of the field as anybody ever looks at in any eyepiece. The advantage of UWA eyepieces is being able to look at details of objects off center as well. If the field is very good to great to the edge you can follow a planet to the edge enjoying a long period of time looking without needing to nudge an undriven scope. If your using a driven scope looking at large objects (Moon, nebula, clusters, etc...) then the UWA designs permit you to look around at leasure at the field looking for details in different areas while still having those parts of the object you may not be looking directly at there for you to enjoy at a whim. Even with an Ortho eyepiece your eye still sees out the same distance, it just doesn't see anything but black outside of the image area. Some people enjoy that framing of the object in darkness, others don't.

It's up to the individual to decide what they enjoy and trying to tell people the extra field is useless is like telling people that a bigger engine is useless in their car or truck. That's for the individual to decide, not for you or anybody but the individual.


Post Extras: Print Post   Remind Me!   Notify Moderator  
pbsastro
professor emeritus
*****

Reged: 03/21/07

Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: tmbuser6]
      #5047574 - 01/31/12 10:12 AM

Quote:


Mr. Black, et al., I think the matter is a bit more complicated than you may realize. You see, it is already well established that the ES-100 design is at least /very/ similar to that of the Ethos, at least according to x-ray analysis. Basically, these eyepieces work with a negative-power Smyth lens group /ahead/ of the field stop, which is internal, about half way to the next lens, which is a positive meniscus. These 4 lenses operate together as a powermate-like group with the field stop placed within the group after the third lens.

Look at the bottom of any of these eyepieces and you will see that there is no external field stop present like in a normal eyepiece, and if you bring your finger up to the field lens while looking through, you will not find any point where you can bring your finger into focus looking thorough the eyepiece! That is because the focal plane is well inside.




True.

Quote:


It is this group which is both essential to and really the basis for the performance of the eyepiece. Due to the negative power of the Smyth lens group and the placement of the focal plane and field stop inside where they must be, the aperture of the Smyth group must be /larger/ than the field stop aperture. If you look hard into the bottom of one of these eyepieces, you may be able to tell that.




Completely false!
What do you mean look hard into the bottom? You just need to measure it with a ruler:
Ethos 17 Ė filed stop =29.6, filed lens =29.6
Nagler 5 and 7 both have field lens **smaller than field stop.
As expected, if the Smyth groups acts as a barlow, naturally the rays diverge and therefore the barlow aperture does not need to be larger than field stop.
And then based on this false statement, you repeat again and again the ES eyepiece is compromised and will vignette.

Quote:


The net result of all of this is that this places an upper limit to the maximum focal length of such an eyepiece to be around 22mm if you wish to not have any vignetting. So, unless Explore has reinvented optics (I don't expect that to be the case), the only other option I can see is to allow for some vignetting to take place.

There were a great many people hoping for a 100 degree Ethos from TeleVue that was long enough to take the place of the 31mm Nagler so that they could retire that eyepiece in favor of an all-Ethos line of eyepieces, and they were hoping for something like a 24-25mm for that purpose, but the practical limit of the design without making compromises was 21mm due to the confines of a 2" barrel, that is why they didn't make it any longer. In order to make a longer focal length, you would need to go to a larger barrel.

And I suspect that was a similar constraint in ES choosing 20mm for their very similar eyepiece. SO, either Explore has chosen to allow a considerable amount of vignetting to occur in the periphery, or they have departed greatly from the original design, which I do not see happening while also maintaining equal performance. Therefore, we do not really know what we are buying here and I myself would be a bit hesitant to invest in one blindly before others have had a chance to sample the eyepiece and evaluate it.

The one maxim that holds true for all of optics is that there are no free lunches: You do not gain in one area without giving something up somewhere else. For ES to have crossed the 22mm threshold still within the limits of a 2-inch barrel, they must have made some compromises elsewhere. ;^)

I would expect the eyepiece to likely have both visible vignetting (limb-darkening around the edges), not be a true 100-degree AFOV, and/or probably have a loss of eye relief (smaller eye lens) as a consequence, which is already at a minimum in the present ES design.

Regards,

Wayne




Post Extras: Print Post   Remind Me!   Notify Moderator  
Scott in NCAdministrator
80mm Refractor Fanatic
*****

Reged: 03/05/05

Loc: NC
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: Darenwh]
      #5047604 - 01/31/12 10:33 AM

Quote:

It's my hobby but she likes going out with me. Still, I will be in the dog house but a few days in the dog house is a small price to pay for such grand views...




Then here's what you have to do. Tell you that you've got some jewels for her birthday, and then show her the Double Cluster through your new EP. Of course you realize that you're going to have to have some real jewelry to surprise her with after that, lest she whomp you over the head with your OTA!


Post Extras: Print Post   Remind Me!   Notify Moderator  
pbsastro
professor emeritus
*****

Reged: 03/21/07

Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: tmbuser6]
      #5047632 - 01/31/12 10:46 AM

I prefer TV to ES, and if TV announces an Ethos 25 or similar till April, I will buy it instead of the ES. However...

Quote:


I've used hundreds of eyepieces over 46 years, I have yet to have any of them fog up for not being purged or sealed with o-rings.




I have only TV eyepieces , not ES eyepieces, but my Ethoses and Naglers sure fog several times every time. I can not confirm that purging would avoid it, but fogging sure is a problem.

Quote:


I think your assessments above are indeed quite accurate, and it will be interesting to read from those who plunk down $1000 and $500 on two really unknown and untested designs from a company which has, to date, seemingly built most of its laurels on the work of others, making less expensive copies. If we were talking about small sums of money I could understand it, but now we are talking about people pre-ordering a ONE-THOUSAND DOLLAR eyepiece that no one has ever even seen yet? And a $500 25mm eyepiece that TeleVue themselves would not build? Yes, expect to pay about $500 for it.




So, ES is to blame when copying other designs, but is also to blame when coming with new designs because they copied some in the past. Sure ES 120 and ES 25 are derivate from Ethos, but also most of TV eyepieces (Plossls, Naglers, etc) are derivate from other designs.

Quote:


Frankly, it amazes me that when the 13mm Ethos came out in the fall 2008, most people were denouncing them as a gimmick, unnecessary and vastly too large, heavy and expensive; now folks are racing to enthusiastically buy a $1000 3 pound eyepiece with twelve lenses in it. That is like stacking an Abbe Ortho on top of another Abbe Ortho on top of another. But if anyone did that, they would be considered crazy, not revolutionary ;^)

The idea of a 7 or 8 element eyepiece has been around for a long time, but a 12-element design? That is a telephoto camera lens! That is four-fold the complexity of an 8-element design. Do you think there will be some ghosting issues and other losses there? ;^)




You mean 12-element like the Nikon HW which is better than Ethos?
Funny, when TV came up with 9-element Ethos several people made the same comments you made now.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jim Romanski
Carpal Tunnel
*****

Reged: 01/02/05

Loc: Guilford, Connecticut
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: rockethead26]
      #5047699 - 01/31/12 11:20 AM

My impression of Explore Scientific is very similar to the way Meade used to operate. I guess that should be no surprise since Scott Roberts is the former VP at Meade Instruments.

Meade used to copy and clone Televue eyepieces. They claimed to have a slightly different design goal but they were pretty darn close to Naglers. Of course to try and distinguish themselves from Televue they made slightly different focal lengths and instead of 82 degrees AFOV they claimed to have 84 degrees.

So ES comes out with 82 degree and then 100 degree eyepieces. Based on disassembly and x-ray of some units it seems pretty obvious they cloned the Ethos. Televue says yes you can reverse engineer their eyepieces and get the glass types and curves right but itís nearly impossible to copy the coatings. Televue states that not only do they use coatings to reduce reflections but they also use them to ďtuneĒ color correction. Possibly one of the reasons that people find ES eyepieces close but not quite as good as Televue.

Quote:

The Ethos SX design at 110 degrees is just beyond the eye's range to see all at once. I see the 9mm 120 degree design as ponderously heavy and essentially pointless as no one will ever be able to see the entire FOV at once,




I can see the entire field in my Ethos SX and the field stop at once. I donít think Iím the only one. So I donít agree with you that 120 degrees is pointless. I want more field if I can get it and itís of good quality. However, I have to wonder how good it is. The ole 13mm Nagler was stopped down to 82 degrees but I believe the original patent is for 90 degrees. I bet you can see 100 degrees in one without the field stop. People used to take them out but the image quality starts to degrade sharply after 82 degrees or so. I bet the Ethos SX can go to 120 degrees too but what does the final 10 degrees look like. Has anyone ever received or looked through an ES 9mm 120 degree eyepiece?

Quote:

Quote:

I've used hundreds of eyepieces over 46 years, I have yet to have any of them fog up for not being purged or sealed with o-rings.




But, as reported here on CN, others have.




Well just because itís happened to a few people doesnít make this a very important feature. Mind you, I donít think itís a gimmick. I think itís a legitimate feature but not of much value to me. If two eyepieces were identical and of equal price why not buy the nitrogen purged one. But if it cost even a few bucks more Iíd pass.

Canon and Nikon make some magnificent camera lenses with far more than 12 glass elements so Iím sure it can be done with an eyepiece.

But until we actually have a 120 degree eyepiece to look through itís speculation as to whether or not it renders a quality field of view. Thatís what counts.

ES like Meade of old seems to be trying to distinguish itself from Televue by one-uping them with the 120 degree field and the 25mm 100 degree eyepiece. But Iíll be surprised if the 25mm does not vignette. I have to wonder if it even exists yet since there are no pictures. Listing the weight as just a bit heavier than their 20mm doesnít convince me that they even have a working prototype. But theyíve been able to bring products to the marketplace thus far so Iím willing to wait and see.


Post Extras: Print Post   Remind Me!   Notify Moderator  
tmbuser6
sage
*****

Reged: 07/01/11

Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: Darenwh]
      #5048223 - 01/31/12 03:34 PM

Quote:

Per Wiki the eye can see in each direction at least 60 degrees so 120 degree eyepieces should be fine for the eye.




Hmm. I have exceptional vision and peripheral sensitivity. If I look on axis through an SX, I cannot catch the field stop, but catch the stop in an Ethos easy. Seems to me you would have to have extraordinary FOV perception in order to be able to catch a 120 degree stop! Perhaps it something to do with the shape of the eye socket or face?

Regards,

Wayne


Post Extras: Print Post   Remind Me!   Notify Moderator  
tmbuser6
sage
*****

Reged: 07/01/11

Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: pbsastro]
      #5048268 - 01/31/12 04:02 PM

Quote:

Completely false!
What do you mean look hard into the bottom? You just need to measure it with a ruler:
Ethos 17 Ė filed stop =29.6, filed lens =29.6
Nagler 5 and 7 both have field lens **smaller than field stop.
As expected, if the Smyth groups acts as a barlow, naturally the rays diverge and therefore the barlow aperture does not need to be larger than field stop.
And then based on this false statement, you repeat again and again the ES eyepiece is compromised and will vignette.




I am sorry if you misunderstood me. You cannot reach the field stop with a ruler to measure it. The Ethos is not a Nagler, my statements are based upon the actual disassembly of an Ethos and a comprehensive ray tracing of the design by Roger Cergioli under the supervision of Dr. Richard A. Buchroeder, Ph.D.; I will let them know they were wrong. But is not the result still the same, as I just measured the field lens in the 21mm Ethos (since we are really talking about going wider) and it looks to be about 38.5mm, as large a lens as will fit within the barrel! So the inevitable result of increasing the focal length in any regard would still seem to be a vignetting of the peripheral field by a 25mm using a similar design. And other designs out there like the Koeler have inferior off axis performance.

Regards,

Wayne


Post Extras: Print Post   Remind Me!   Notify Moderator  
Smithfr2000
member


Reged: 09/12/09

Loc: Nantes - France
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: tmbuser6]
      #5048276 - 01/31/12 04:08 PM

Quote:

But Iíll be surprised if the 25mm does not vignette




Is it the physical limit of the EP design which would produce vignetting, or the fully illuminated field which would be too small for most of the scopes ?

Edited by Smithfr2000 (01/31/12 04:10 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
tmbuser6
sage
*****

Reged: 07/01/11

Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: pbsastro]
      #5048295 - 01/31/12 04:18 PM

Quote:

I have only TV eyepieces , not ES eyepieces, but my Ethoses and Naglers sure fog several times every time. I can not confirm that purging would avoid it, but fogging sure is a problem.




I am surprised to hear that. I have never had internal fogging of an eyepiece or seen it by anyone else at a starparty.

Quote:

You mean 12-element like the Nikon HW which is better than Ethos?




Well, first of all, better by whose assessment? The optics in the Ethos are essentially perfect and if I add a Powermate to my apo using the 13mm Ethos, I can no longer see any difference between the periphery and the center field at all! So any improvement would have to be very, very minor. THe Nikon does use a larger eye lens so I understand it would have even better eye relief.

Second, if I ever have an issue with an Ethos, I can drive to TeleVue and they will fix it for me. The Nikon is, last I checked, about TWICE or THREE TIMES the cost of an Ethos! I love my optics but no eyepiece is worth that much to me for such a small improvement! Truly, the emperorís robes! ;^)

Regards,

Wayne


Post Extras: Print Post   Remind Me!   Notify Moderator  
dyslexic nam
Carpal Tunnel
*****

Reged: 01/28/08

Loc: PEI, Canada
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: tmbuser6]
      #5048426 - 01/31/12 05:34 PM

I find it interesting that you can label an Ethos as optically 'essentially perfect' (and admit to using one), while you feel justified in labeling the forthcoming ES ep's as a 'garish design'. It is that lack of objectively - coupled with a complete lack of empirical data regarding the new ES offerings - that tends to get people a bit annoyed. At least it annoys me. And you certainly aren't the only one on CN who has these tendencies.

I get that Nagler has done a lot for astronomy. Kudos to him. I assume he has been compensated for his efforts. But there seems to be a group of people on here that seem to think 'uncle Al' has exclusive domain on ep innovation. At least that is the impression I get from reading many of those posts.

In fairness, it is true that ES seems to have based their current ep lines on existing designs. But given their demonstrated ability to produce quality optics, I am willing to give them the benefit of the doubt when it comes to their announced offerings. I may be proven wrong, but I know that I don't feel justified is assuming that their new ep's will be garish designs suffering from vignetting and fatal design compromises.


Post Extras: Print Post   Remind Me!   Notify Moderator  
JMW
Pooh-Bah


Reged: 02/11/07

Loc: Nevada
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: dyslexic nam]
      #5048602 - 01/31/12 07:07 PM

I am excited enough about a 25MM ES 100 that I placed the preorder. My Ethos 21 is my favorite eyepiece. The 25 will fill the place between my Ethos 21 and my Naglar 31T5. Using wide field eyepieces under very dark sky's with our clubs Obsession 20 inch F5 is my favorite way to observe.

Post Extras: Print Post   Remind Me!   Notify Moderator  
bherv
Carpal Tunnel
*****

Reged: 03/10/06

Loc: WMass
Re: 25mm ES 100* confirmed? sale date? preorder? [Re: dyslexic nam]
      #5048612 - 01/31/12 07:14 PM


Well put. I have been very happy with my ES eyepieces and have compared the view with some Televue eyepieces and found the difference negligible. Yes Televue eyepieces are top notch but many of us just can't afford to shell out $600 on an eyepiece.
Barry


Post Extras: Print Post   Remind Me!   Notify Moderator  
pbsastro
professor emeritus
*****

Reged: 03/21/07

Re: 25mm ES 100* confirmed? sale date? preorder? [Re: tmbuser6]
      #5048641 - 01/31/12 07:29 PM

Quote:

Quote:

Completely false!
What do you mean look hard into the bottom? You just need to measure it with a ruler:
Ethos 17 Ė filed stop =29.6, filed lens =29.6
Nagler 5 and 7 both have field lens **smaller than field stop.
As expected, if the Smyth groups acts as a barlow, naturally the rays diverge and therefore the barlow aperture does not need to be larger than field stop.
And then based on this false statement, you repeat again and again the ES eyepiece is compromised and will vignette.




I am sorry if you misunderstood me. You cannot reach the field stop with a ruler to measure it. The Ethos is not a Nagler, my statements are based upon the actual disassembly of an Ethos and a comprehensive ray tracing of the design by Roger Cergioli under the supervision of Dr. Richard A. Buchroeder, Ph.D.; I will let them know they were wrong. But is not the result still the same, as I just measured the field lens in the 21mm Ethos (since we are really talking about going wider) and it looks to be about 38.5mm, as large a lens as will fit within the barrel! So the inevitable result of increasing the focal length in any regard would still seem to be a vignetting of the peripheral field by a 25mm using a similar design. And other designs out there like the Koeler have inferior off axis performance.

Regards,

Wayne




I state that you are spreading false information about field lens aperture and field stop, two things that anyone can easily check, and you come talking about ray-tracing and PhDs?
Field lens is easy to measure with a ruler, no need to open eyepiece. Field stop is given by Televue in TV site.

You donít need to put any lens inside the 2Ē barrel. Pan 35 is 2Ē eyepiece and does not have any lens inside 2Ē barrel. So you can have a 2Ē Ethos with a 46mm clear aperture field lens, the lens can be outside the 2Ē barrel, it will just require extra infocus.
So with 46mm clear aperture field lens you can have a 2Ē 26mm Ethos, it is a fact no one can dispute. The only thing people can say is that it will need more infocus as all the lenses need to be outside 2Ē barrel. In the end it is the same as some TV eyepieces with 2Ē lenses but with 1.25Ē barrel.


Edited by pbsastro (01/31/12 07:54 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
tmbuser6
sage
*****

Reged: 07/01/11

Re: 25mm ES 100* confirmed? sale date? preorder? [Re: dyslexic nam]
      #5048696 - 01/31/12 08:08 PM

Quote:

I find it interesting that you can label an Ethos as optically 'essentially perfect' (and admit to using one), while you feel justified in labeling the forthcoming ES ep's as a 'garish design'.




Hey, I didn't label the Ethos as essentially perfect optics, that is a direct quote from some of the leading optical experts in the industry! I just happen to agree with them. And as far as "objectivity" and "annoyance" and garish, I was referring to my own opinion of someone needing or wanting to put twelve lenses into an eyepiece to look at something. I never said I was being "objective," your annoyance is at your own hands and not my doing because folks read more into words than what was actually said.

Regards,

Wayne


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | (show all)


Extra information
10 registered and 23 anonymous users are browsing this forum.

Moderator:  ausastronomer, droid, Scott in NC 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 20237

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics