100 deg EPs to glass wearers?

[DaniAstro]

A lot of posts for 1 week which makes me happy. This new old 100 degree series of MEADE is telling me that somebody is working in the right directions now. As now MEADE is owner of China company and has all the access to China eyepiece making technology/manufacturers and China;s prices MEADE has to offer similar eyepieces as spec and price ot that of Explore Scientific. I don't think that at the moment they have the capacity to offer an eyepiece of the optical quality of Televue.

As Alan has testes the 82 degrees ES eyepiece he is not very happy of if. But the price is really nice. So as usual you get whatyou paid for.

Good think about MEADE being a China company will be that prices of good eyepieces and equipment (middle price range and quality) will go lower as three mayor China telescope manufacturer are competing in USA and the world - Synta, ES/Bresser/JOC and MEADE.

As I told Alan - ES are preparing a 3" eyepiece and diagonal pushing further up the boundery. This means that they are intesting in the products that is good for all of us consumers.

Before 5 years 100 degrees was like a dream. Now is standard and the new 110 and 120 degrees will become standard. This is good evolution taking into consideration the small market and how much is intested in astronomical optics. 

I also heard of a new technology of making the lens of the refractors - on CNC machines which if going massive the make the price of APOs plunge. I guess something similar in mass making of eyepieces is what is causing the boom in production of new types of eyepiece.

Please excuse the long post.

[bomberbaz]

Somewhere earlier in this thread someone mentioned al nagler said ER could not be extended beyond 15mm as this would start to detract from the quality of the eyepiece.

If meade really have achieved the 20mm ER has they are claiming, what is it that is going to give. Are you potentially losing light transmission, coma, pincushion? Just wndered if anybody might have any thoughts on what might occur (emphasis on might)

Of course the views might be perfect although we shall wait and see although in case you hadnt guessed i am very interested ;-)

[John]

Somewhere earlier in this thread someone mentioned al nagler said ER could not be extended beyond 15mm as this would start to detract from the quality of the eyepiece.

If meade really have achieved the 20mm ER has they are claiming, what is it that is going to give. Are you potentially losing light transmission, coma, pincushion? Just wndered if anybody might have any thoughts on what might occur (emphasis on might)

Of course the views might be perfect although we shall wait and see although in case you hadnt guessed i am very interested ;-)

It's my suspicion that 15mm is around the max for a 100 degree eyepiece but I've not got the optical know-how to explain why that is and someone may well prove me incorrect - in which case good for them

Tele Vue managed to push the eye relief out with the T4 Nagler series without sacrificing image quality or FoV so it might be possible I guess.

If you use a 100 degree eyepiece with a barlow it will increase the eye relief of course.

[michael.h.f.wilkinson]

My suspicion is that the eye lens needs to be excessively large for longer eye relief. As I see it, the minimum eye lens diameter would be the diameter of the exit pupil plus the eye relief multiplied by twice the sine of the half AFOV angle (50 deg for ean Ethos 36 for a Delos). For 7mm exit pupil, 15mm eye relief and 100 deg AFOV, we arrive at about 30mm diameter. For the Delos we have 20mm ER, and 72 deg AFOV, and the figure becomes 30.5mm. Extending the ER of an Ethos-like EP to 20mm gives 37.6mm eye lens, or 25.56% more (linearly). This would mean at least 57% more glass (calculated by surface area) or 98% more if we have to scale the thickness of the lens in the same way as well.   Choosing a smaller eye lens would lead to vignetting, which rather defeats the purpose of an ultra-wide angle.

A large eye lens would also scale up many lenses behind it, leading to major headaches in terms of weight and size

[bomberbaz]

A large eye lens would also scale up many lenses behind it, leading to major headaches in terms of weight and size

Having a look at the Delos 14mm, this weighs in at  14.4oz where as the 15mm Meade MWA comes in at 22.8, oz so its backs up that part of your assumption michael.

So given what you are saying above, are we probably looking at a eyepiece that requires a fair amount of eye and probably head movement to take advantage of the full available TFOV of these eyepieces?

Steve

[michael.h.f.wilkinson]

Having a look at the Delos 14mm, this weighs in at  14.4oz where as the 15mm Meade MWA comes in at 22.8, oz so its backs up that part of your assumption michael.

So given what you are saying above, are we probably looking at a eyepiece that requires a fair amount of eye and probably head movement to take advantage of the full available TFOV of these eyepieces?

Steve

Not sure really. Some eye movement to really take in the views are needed to some extent in the Naglers and in Olly's Ethos. These should not necessarily be much different

[YKSE]

A large eye lens would also scale up many lenses behind it, leading to major headaches in terms of weight and size

I assume that's good reasons for  the 100 deg EP don't have longer ER, another reason is that not all astronomers wear glasses.

As to minimum eye lens diameter and ER, this is simple trigonometry, as seen in the picture below:

Where D is the eye lens diameter, ER is eye relief, alfa is the AFOV of eyepiece, we have the relation

D/2=ER*sin(alfa/2)

or D=2*ER*tan(alfa/2)

for 100 deg eyepiece with 20mm ER, we get

D= 2*20*tan(100/2)=40*tan50=46.7mm

This is the minumum (flat)eye lens size without vignetting, it could be smaller if the eye lens is recessed.

Edit:

Taking Ethos as an example:

15mm ER requires min eye lens is

D=2*15*tan50=35.8mm.

[michael.h.f.wilkinson]

I assume that's good reasons for  the 100 deg EP don't have longer ER, another reason is that not all astronomers wear glasses.

As to minimum eye lens diameter and ER, this is simple trigonometry, as seen in the picture below:

2014-12-19 14-45-21.png

Where D is the eye lens diameter, ER is eye relief, alfa is the AFOV of eyepiece, we have the relation

D/2=ER*sin(alfa/2)

or D=2*ER*tan(alfa/2)

for 100 deg eyepiece with 20mm ER, we get

D= 2*20*tan(100/2)=40*tan50=46.7mm

This is the minumum (flat)eye lens size without vignetting, it could be smaller if the eye lens is recessed.

Edit:

Taking Ethos as an example:

15mm ER requires min eye lens is

D=2*15*tan50=35.8mm.

You are right: it should be the tangent of alpha not the sine

[bomberbaz]

lost me completely lads sorry   

[jetstream]

Seems pretty easy for Televue to do then, although with more weight and cost. It could be a good marketing strategy really, letting Meade etc test the waters before a huge T2 Ethos release. I was wondering why the Ethos retail price has been sneaking down... I presume the Ethos is a high markup piece, insulating TV from competitors a bit, and they sell a pile of them already.

If that eyelens on the Meade is undersized, they are flawed already, vignetting maybe? A good review is needed before any purchases of the Meade IMHO and as others have stated.

[jetstream]

I assume that's good reasons for  the 100 deg EP don't have longer ER, another reason is that not all astronomers wear glasses.

As to minimum eye lens diameter and ER, this is simple trigonometry, as seen in the picture below:

2014-12-19 14-45-21.png

Where D is the eye lens diameter, ER is eye relief, alfa is the AFOV of eyepiece, we have the relation

D/2=ER*sin(alfa/2)

or D=2*ER*tan(alfa/2)

for 100 deg eyepiece with 20mm ER, we get

D= 2*20*tan(100/2)=40*tan50=46.7mm

This is the minumum (flat)eye lens size without vignetting, it could be smaller if the eye lens is recessed.

Edit:

Taking Ethos as an example:

15mm ER requires min eye lens is

D=2*15*tan50=35.8mm.

Yong, are there other eyepiece design considerations along its optical path that determine the eyelens diameter or does this eye relief calculation satisfy all requirements?

[YKSE]

Yong, are there other eyepiece design considerations along its optical path that determine the eyelens diameter or does this eye relief calculation satisfy all requirements?

Well, if we're very pernickety, we should add the size of exit pupil to the above calculated value, the reason is that all the lights from edge doesn't converge to one single point, it converge to form the exit pupil. so the light from edge only converge to the edge of exit pupil. A 20mm 100 deg EP will have about 3mm bigger eye lens than 5.5mm 100 deg EP, because the exit pupil in the 20mm will be about 3mm bigger, if the two EPs are having the same ER.

All these are about the ER and eye lens size, as to questions about aberations, such as astimatism, lateral color, etc, are much more complicated optical issues, nothing for simle mathematical solution.

[jetstream]

Good to know, I was wondering when "minimum" eye lens diameter was mentioned and wondered what the "optimum" eye lens dia might be, but maybe there are other considerations that effect it.

[russ.will]

I know Unc Al said; But if there's one thing I've noticed in the various forms of technology in which I dabble, then it is that today's master is tomorrows past master.

That in no way denigrates their achievements, which without doubt raised the standard, to that which then became the benchmark. The designs of eyepieces are littered with the names of those dreamers, innovators and now, past, past masters. However, the masters of tomorrow stand on the shoulders of the giants of today, as in any branch of science and technology and when you're talking about China, they have 1/4 of the world's population to source that one, individual and incredible talent from.

They have an economy of scale and pool of potential talent the West can only dream of. Whilst the assertions of Mr. Nagler are true with respect to the current state of the manufacturing art, the future will surpass these limits. Future eyepieces, WILL have wider fields of view, WILL have longer eye relief, WILL be better corrected and WILL be cheaper. Technological manufacturing limitations that fix the current status quo, WILL be overcome. The last twenty to thirty years of development in this hobby and the rate at which technological advance is accelerating, give no grounds to suspect this will not be so.

Whether the Meade Mega Wides will be that quantum leap, is of course pure conjecture at this point. But to my mind, it's that end of the globe that is statistically more likely to deliver it, WHEN it happens and wherever it happens, it is certain that it definitely will.

This is also why I get the slight hump when I hear discontent around cloned designs. In every other branch of science and technology, you make your breakthrough and profit from your lead whilst you can, understanding that others will learn from it. Competitors will try to build on it and deliver something better and/or cheaper. This is also a break-through. As far as I am aware, nobody is doing any of this for purely altruistic motives and competition that delivers the value we all crave is built purely on the understanding that your competitors will catch up. That is entirely natural and will not and should not, change.

Russell

[John]

Very interesting post Russell and I tend to agree. In due course somebody else will take up the baton of progress and move things on.

On the topic of these new Meade eyepieces, the thread on "Cloudynights" is developing quite a degree of expecation and excitement with one member now having the 21mm in his hands ready for testing. Here it is for anyone interested:

http://www.cloudynights.com/topic/485277-meade-series-5000-mwa-has-arrived/page-3#entry6354115

24 hours from now we may see the classifieds full of Ethos / Ethoi / Ethe !

[alan potts]

John,

Some interesting words on CN from the guy calling himself Starman who I think is Don Pensack, I can't help wonder if this is going to be a supernova or a damp squib.

[estwing]

Very interesting post Russell and I tend to agree. In due course somebody else will take up the baton of progress and move things on.

On the topic of these new Meade eyepieces, the thread on "Cloudynights" is developing quite a degree of expecation and excitement with one member now having the 21mm in his hands ready for testing. Here it is for anyone interested:

http://www.cloudynights.com/topic/485277-meade-series-5000-mwa-has-arrived/page-3#entry6354115

24 hours from now we may see the classifieds full of Ethos / Ethoi / Ethe !

..not mine you won't!!....I hope there great ep's...but proof is in the pudding

[alan potts]

This is a slight sidetrack to thread topic but Ethos has cropped up a few times. It is only just now after a period of about 20 months with the 21mm that I am beginning to warm to it. I was forever taking the 20mm Nagler outside with me. The 20mm, plus or minus a bit, is a most useful F/L and I really am now beginning to see just how good the big boy of the Ethos band is, though many of you have been telling me this for a long time. 

[YKSE]

24 hours from now we may see the classifieds full of Ethos / Ethoi / Ethe !

I'm not sure I see this happening.

Even if Meades new MWAs deliver the optical quality as good or nearly as good as Ethos, and by the specification given, 15mm ER is perfectly all right for none glass-wearers, and for some glass-wearers too.

The best Meade MWA can do is provoding most glass-wearers with 100 deg EPs, in my world, most of them don't have Ethos yet assuming that they know they need 20mm ER.

[russ.will]

24 hours from now we may see the classifieds full of Ethos / Ethoi / Ethe !

If history shows us another thing, it's that you won't change the minds of TV owners that quick, if at all!

Russell

[russ.will]

The best Meade MWA can do is provoding most glass-wearers with 100 deg EPs, in my world, most of them don't have Ethos yet assuming that they know they need 20mm ER.

That would be progress.

Russell

[alan potts]

Russell,

Have you not compared the edge sharpness of your 17.3mm Delos and the 20mm Maxvision in your Dobsonian, I know one costs a great deal more than the other but they are not the same. I for one would welcome with open arms an eyepiece that gives the same degree of overall quality for half the price at F5 but I am still to see one and I get to see a few of the so called better quality eyepieces.

Alan.

[bomberbaz]

The best Meade MWA can do is provoding most glass-wearers with 100 deg EPs, in my world, most of them don't have Ethos yet assuming that they know they need 20mm ER.

I am not sure I agree with you here, if the Meade is A) up to the job and less than half the price of an Ethos then I see a large number of them being snapped up by people who have previously shy'd away because of the price of the Ethos and a good many of them, myself included will be glasses wearers. I also see a number of people although certainly not as many cashing in on the Ethos and getting the lower costing option from Meade.

[estwing]

Or it could force a TV price-cut

[swamp thing]

These are exciting times in the hyper wide world......

I should imagine there are a lot of nervous Ethos owners out there ATM

Personally I don't think they have anything to worry about, I just can't see the Meade holding edge sharpness in big fast scope with that eye relief......Oh but I do hope they prove me wrong. 

Come on Meade