New Takahashi eyepieces announced

[MalcolmM]

Most of the technical voodoo is above my understanding! I want to hear razor sharp, impossible contrast, how can there be so little scatter, my jaw hit the floor when I turned it on Saturn, these things are magic ... 🙂

Malcolm 

[vlaiv]

Technical specs are there for a reason.

Not everyone can afford to purchase expensive eyepiece just to try it out

Not everyone can borrow such eyepiece to try it out

Reviews of the eyepiece contain more information if eyepiece is compared to another eyepiece and differences are outlined. Just saying - "it gives excellent views" does not mean much if we don't have reference / baseline. This can pose the same / similar problem as point one above - not everyone had the opportunity to try comparison eyepiece so they won't completely understand performance based on a difference to unknown.

We often resort to "hive mind" when choosing an item for our next purchase because of the above.

This is why in many fields there is a standard for listing technical specification. People can make informed decision. If an engineer needs a part for a project - they can simply look at the specs with high level of confidence that they will get what they need.

I'm afraid that we are not there yet with astronomical equipment.

[MalcolmM]

I completely agree with everything you say @vlaiv and I'm speaking, sort of tongue in cheek, being a self confessed irrational Takahashi fan 🙂

I do enjoy reading people's experiences with equipment when their enthusiasm bursts through. Even more so when it confirms my bias 🙂

Malcolm 

[IB20]

17 hours ago, Mr Spock said:

What we need is someone gullible enthusiastic enough to test them 

Give me a month or two to sort out my Astro funds… 😅

[John]

Given the weather we have had in the UK lately, practical testing of eyepieces under the stars is getting rather hard to carry out. I have a couple of very interesting eyepieces on loan currently and but it is clearly going to be a long time until I get enough practical experience with them under my belt to write anything meaningful about them on SGL 🤔

With optical standards edging closer and closer between the best and the rest, you need some sessions under good conditions to spot the often subtle but consistent differences between them.

Its getting a bit academic as to whether eyepiece X has a tiny % better light scatter, sharpness or contrast than eyepiece Y if the chances of using the darn things at all is so slim 🙄

Edited July 30, 2023 by John

[vlaiv]

I rather like approach that @Louis D has been championing - shoot view thru the eyepiece with camera. If we fix enough parameters and make sure optics and sensor side are uniform enough and don't interfere as much with performance of the eyepiece - we could develop "a standard" for comparing eyepieces.

Imagine database of images - with EP manufacturers publishing their own shots on new eyepieces. You can simply take two shots - one of the eyepiece you are familiar with and the new one - and you get instant comparison (at least in part) of their performance.

Of course - there are parameters that are going to be individual preference between two eyepieces - but what I'm here saying is that specs don't necessarily need to be in form of numbers and hard to understand graphs - they can be something that we intuitively understand well.

[John]

The "standard" for eyepiece performance has to be how they perform for their intended purpose, with a human at one side and a telescope at the other, observing celestial targets, surely ?

Other data is of interest of course and fuels discussion during unfavourable conditions but the practical experience must have primacy I feel.

Otherwise forums like this will become little more than technical / theoretical interest discussion groups which might appeal to a few but I suspect the majority would much rather be out there "doing it" as often as possible.

[vlaiv]

15 minutes ago, John said:

The "standard" for eyepiece performance has to be how they perform for their intended purpose, with a human at one side and a telescope at the other, observing celestial targets, surely ?

Of course. Nothing beats actual use, but I was referring to the specification.

Say you want to purchase a new eyepiece. Focal length, eye relief, AFOV and/or field stop diameter (hopefully) will be listed - and these all impact our purchasing decision. Now, wouldn't it be nice if you had the image of what you might expect in terms of sharpness as well?

All of the above won't guarantee that you'll enjoy that eyepiece in your scope given your observing style and preferences - but it is important part of decision making process when you want to select eyepiece to try out.

In my view - such image would certainly beat any sort of spot diagram or number that you can't really easily relate to the expectation of what the view thru such eyepiece will be like.

Think of it this way - you plan a holiday and want to select your accommodation. Sure, you'll get all the info - number of rooms, square footage, view overlooking the bay (if it is a sea resort) facing west, bed size - you name it.

Then there are photos of the accommodation and the view - which would you prefer - written specs or images?

And certainly - photos can't really entirely show you the feeling of staying in such accommodation - you need to experience that for your self - but they are much better indicator of what to expect then just a list of numbers and facts, right?

[John]

Look at where the eyepiece sits in Suiters "wobbly stack" of factors that impact the quality of the view - way down the list.

How could any image indicating possible eyepiece sharpness take account of all the other things, external to the eyepiece, that will impact that ?

It would be a nightmare for vendors as well - so many returns when observers views are not quite what the advertised image fidelity seemed to promise.

I agree that consistently accurate information on eyepiece specifications would be good though. So often AFoV and actual eye relief figures (even focal length occasionally) are inaccurate and field stop diameters are often missing altogether.

Anyway, this is straying off the topic of the new Takahashi eyepieces so I'll leave it there and wait for some reports from those who are actually using them under the stars. There are some starting to filter through on the CN forum.

 

 

 

 

Edited July 30, 2023 by John

[Louis D]

5 hours ago, Mr Spock said:

How about we do the old fashioned thing and look through stuff instead of getting tied up on technical voodoo 

Sounds like we have a volunteer to take one for the team. 😁

Let us know what you think of them.

[Don Pensack]

2 hours ago, John said:

Look at where the eyepiece sits in Suiters "wobbly stack" of factors that impact the quality of the view - way down the list.

How could any image indicating possible eyepiece sharpness take account of all the other things, external to the eyepiece, that will impact that ?

It would be a nightmare for vendors as well - so many returns when observers views are not quite what the advertised image fidelity seemed to promise.

I agree that consistently accurate information on eyepiece specifications would be good though. So often AFoV and actual eye relief figures (even focal length occasionally) are inaccurate and field stop diameters are often missing altogether.

Anyway, this is straying off the topic of the new Takahashi eyepieces so I'll leave it there and wait for some reports from those who are actually using them under the stars. There are some starting to filter through on the CN forum.

 

 

 

 

The problem comes when someone gives a review of an eyepiece in an f/8 refractor and only cares about the sharpness in the center 1/3 of the field.

The person who has an f/4 dob and is looking for sharpness from edge to edge who reads that review has not read a review relevant to his scope or requirements.

And perhaps the reviewer hasn't looked through hundreds of eyepieces and doesn't have the experience to really review the eyepiece.

Merely stating that it was good doesn't carry any weight, in that case.

So some form of a review that contains measurements, even if it is above the heads of most readers of the review, is really essential.  We just don't get that 95% of the time.

I want to see at LEAST the following in a review.  We won't get it, though, because there is too little profit in eyepieces to pay for the necessary testing and too little interest

in knowing the results of such testing.:

1.       spherical aberration_________________________________________________________

2.       coma_____________________________________________________________________

3.       astigmatism________________________________________________________________

4.       field curvature______________________________________________________________

5.       distortion--type and amount___________________________________________________

6.       chromatic aberration--axial and lateral___________________________________________

7.       apparent field_______________________________________________________________

8.       eye relief___________________________________________________________________

9.       light scatter control--field and star outside field (glare)______________________________________________________________________

10.   SAEP_______________________________________________________________________

11.   CAEP_______________________________________________________________________

12.   Tint or spectrum of transmission________________________________________________________________________

13.   Vignetting___________________________________________________________________

14.   Transmission_________________________________________________________________

15.   thermal issues________________________________________________________________

16.   field stop focus_______________________________________________________________

17.   impression of contrast_________________________________________________________

18.   EOFB_______________________________________________________________________

19.   Sharpness on axis/50%/edge____________________________________________________

20.   Presentation of field: close, medium, distant________________________________________

21.   Presentation of field: concave (bowl), flat, convex (globe)_____________________________

Other comments about eyepiece_______________________________________________________________________________________________

Edited July 30, 2023 by Don Pensack

[JeremyS]

42 minutes ago, Don Pensack said:

The problem comes when someone gives a review of an eyepiece in an f/8 refractor and only cares about the sharpness in the center 1/3 of the field.

The person who has an f/4 dob and is looking for sharpness from edge to edge who reads that review has not read a review relevant to his scope or requirements.

And perhaps the reviewer hasn't looked through hundreds of eyepieces and doesn't have the experience to really review the eyepiece.

Merely stating that it was good doesn't carry any weight, in that case.

So some form of a review that contains measurements, even if it is above the heads of most readers of the review, is really essential.  We just don't get that 95% of the time.

I want to see at LEAST the following in a review.  We won't get it, though, because there is too little profit in eyepieces to pay for the necessary testing and too little interest

in knowing the results of such testing.:

1.       spherical aberration_________________________________________________________

2.       coma_____________________________________________________________________

3.       astigmatism________________________________________________________________

4.       field curvature______________________________________________________________

5.       distortion--type and amount___________________________________________________

6.       chromatic aberration--axial and lateral___________________________________________

7.       apparent field_______________________________________________________________

8.       eye relief___________________________________________________________________

9.       light scatter control--field and star outside field (glare)______________________________________________________________________

10.   SAEP_______________________________________________________________________

11.   CAEP_______________________________________________________________________

12.   Tint or spectrum of transmission________________________________________________________________________

13.   Vignetting___________________________________________________________________

14.   Transmission_________________________________________________________________

15.   thermal issues________________________________________________________________

16.   field stop focus_______________________________________________________________

17.   impression of contrast_________________________________________________________

18.   EOFB_______________________________________________________________________

19.   Sharpness on axis/50%/edge____________________________________________________

20.   Presentation of field: close, medium, distant________________________________________

21.   Presentation of field: concave (bowl), flat, convex (globe)_____________________________

Other comments about eyepiece_______________________________________________________________________________________________

Do I detect a retirement project coming on, Don? 😊

[Don Pensack]

On 29/07/2023 at 02:21, vlaiv said:

That is not quite what I've said (nor was it claimed by Tak).

I'll need a bit of an introduction that you and anyone else reading this explanation may already know - then consider this as a reminder and setting the context for what will be said.

Telescope is a projection device - it projects angles onto a focal plane.

Eyepiece is "inverse" of above - it takes image from focal plane and turns it into output rays at certain angles.

When we combine the two we get system that magnifies the image - or increases incident rays by some factor.

To understand what I meant by factor of x287 over airy disk of F/10 scope

we need to think of eyepiece as magnification lens - much like regular magnifying lens.

Whatever is placed at focal plane of eyepiece - we will be able to see it magnified.

Now, back to original TAK diagram and their claim

They claim that single spot at focal plane produces above image. Not star image thru a telescope - but single spot. Think of it as single atom of light emitting phosphorus or something like that in focal plane. That single point will produce object that is up to 4 micro radians to our eyes or 0.825 arc seconds. Now in perfect system - single dot, no matter how magnified will still be single dot - but this eyepiece "blurs" that perfect dot into something that has angular size like say one of the moons of Jupiter - viewed by the naked eye.

Now, let's for the moment say we have perfect eyepiece - one that introduces no aberrations. 4" F/10 telescope will produce airy disk 2.77 arc seconds. Such telescope has 1000mm focal length and if we pair it with perfect 12.5mm eyepiece - image will be magnified by 1000/12.5 = x80

To our eye - star, or rather its airy disk will look like it is 2.77" * x80 = 221.6 arc seconds large

So perfect spot in focal plane with Tak eyepiece will be presented to us like 0.825" large circle (in worst case at edge of the field) while

4" F/10 scope with perfect eyepiece (in fact both can be perfect optical system) - will present star image to our eyes that is 221.6 arc seconds large.

Difference between these two images is 221.6 / 0.825 = x268 (I obviously made a typo or copy error in initial calculation - as result is 268 not 287).

The way one needs to interpret that would be - perfect eyepiece in 4" F/10 scope will produce around 221.6" airy disk size to our eyes, but with Tak eyepiece that size will be increased by roughly 1/268th of that to 222.4" - at the edge of the field.

Or in simple words - blur that eyepiece adds to perfect airy disk (for 4" F/10 scope) is about 1/268 of the size of that airy disk - of we could say insignificant.

Hope this makes sense now.

That is a mistranslation.  The Takahashi illustration says 0.004 rad, which is 4 milliradians, not micro.

[John]

On 30/07/2023 at 14:56, Don Pensack said:

The problem comes when someone gives a review of an eyepiece in an f/8 refractor and only cares about the sharpness in the center 1/3 of the field.

The person who has an f/4 dob and is looking for sharpness from edge to edge who reads that review has not read a review relevant to his scope or requirements.

And perhaps the reviewer hasn't looked through hundreds of eyepieces and doesn't have the experience to really review the eyepiece.

Merely stating that it was good doesn't carry any weight, in that case.

So some form of a review that contains measurements, even if it is above the heads of most readers of the review, is really essential.  We just don't get that 95% of the time.

I want to see at LEAST the following in a review.  We won't get it, though, because there is too little profit in eyepieces to pay for the necessary testing and too little interest

in knowing the results of such testing.:

1.       spherical aberration_________________________________________________________

2.       coma_____________________________________________________________________

3.       astigmatism________________________________________________________________

4.       field curvature______________________________________________________________

5.       distortion--type and amount___________________________________________________

6.       chromatic aberration--axial and lateral___________________________________________

7.       apparent field_______________________________________________________________

8.       eye relief___________________________________________________________________

9.       light scatter control--field and star outside field (glare)______________________________________________________________________

10.   SAEP_______________________________________________________________________

11.   CAEP_______________________________________________________________________

12.   Tint or spectrum of transmission________________________________________________________________________

13.   Vignetting___________________________________________________________________

14.   Transmission_________________________________________________________________

15.   thermal issues________________________________________________________________

16.   field stop focus_______________________________________________________________

17.   impression of contrast_________________________________________________________

18.   EOFB_______________________________________________________________________

19.   Sharpness on axis/50%/edge____________________________________________________

20.   Presentation of field: close, medium, distant________________________________________

21.   Presentation of field: concave (bowl), flat, convex (globe)_____________________________

Other comments about eyepiece_______________________________________________________________________________________________

We can work as a team Don - you handle points 1 - 21 and I'll contribute the "other comments" 😁

[vlaiv]

1 hour ago, Don Pensack said:

That is a mistranslation.  The Takahashi illustration says 0.004 rad, which is 4 milliradians, not micro.

One that I managed to find does not quite say 0.004 rad (It might as well as far as I know), but rather this:

something, something, something 4, something something

436nm~656nm something 11 something something something

It appears that I did not need to look for this - it's been posted on the page 1 of this thread.

But we can do this the other way around as well:

vs

From what I can tell - Japanese text on that image indeed reads the same as google translation of micro radians (I left 0.004 by accident - I typed then number alone first - ignore zeros as text contains 4 and Japanese letters that translate from micro not milli).

[Don Pensack]

Well, something is fishy, because no eyepiece made in the universe puts its spot in a 4 microradian circle.

Milliradians, yes.

And you can see the translation here, also using Google Translate:

https://www.cloudynights.com/topic/883440-new-takahashi-eyepieces-announced/?p=12829217

[vlaiv]

17 minutes ago, Don Pensack said:

Well, something is fishy, because no eyepiece made in the universe puts its spot in a 4 microradian circle.

Well, to be honest - I never saw spot diagram of eyepiece alone - without optics, but if you look at it that way - it is possible to get that small scatter.

Most of the scatter of spots comes from primary optics rather than from eyepiece / or from "interplay" between eyepiece and primary optics.

We could say that above spot diagram is marketing trick because of that - but I do think it is at least somewhat informative.

[Frenchastro]

Netflix's shocking new series 🤠

 

LA CASA DE TPL 🤣...

[Frenchastro]

On 30/07/2023 at 11:02, John said:

Given the weather we have had in the UK lately, practical testing of eyepieces under the stars is getting rather hard to carry out. I have a couple of very interesting eyepieces on loan currently and but it is clearly going to be a long time until I get enough practical experience with them under my belt to write anything meaningful about them on SGL 🤔

So true, same here in Paris, a weather to embark on the study of frogs and snails. Adding to the August holidays, my serious observations will not take place before September. I plan to use them in bino at f15 (foa), and on a turret with the abbe, LE and clavé. We'll see.

[Louis D]

43 minutes ago, Frenchastro said:

Netflix's shocking new series 🤠

 

LA CASA DE TPL 🤣...

Look at how far the eye lens is recessed on the 25mm!  18mm of eye relief gone to waste.  So much for any illusions of me using the 25mm with eyeglasses (low power + strong eye astigmatism = eyeglasses at the eyepiece for me).  It's almost as bad as my 26mm Sirius Plossls.  I have to really cram my eyeglasses against my face to see their meager 50 degree field of view.  Needless to say, I rarely use my pair in my BV.

I guess I'll rely on those of you with either little to no eye astigmatism or who wear contacts to give feedback on these.

[Frenchastro]

I have the chance to observe without glasses. At first sight, on the 25 and 18 it seems to go on. For the 12.5 the ER  is reduced and when you stick the eye you have a little tunnel effect, as usual on the plossl, below 12,5 it's gone starting to get short...Hence the barlow. 

What was essential for me was that I am lucky to have been able to import them from Japan thanks to a friend. They came back to me at 164 € (around £141) all taxes included. In this hobby i quickly understood that it was necessary to have friends all over the world. I send Chablis and Camembert and they send me Takahashi 😅

CS 

[John]

2 hours ago, Frenchastro said:

What was essential for me was that I am lucky to have been able to import them from Japan thanks to a friend. They came back to me at 164 € (around £141) all taxes included.....

That is an excellent price. Does that include import tax / duty or does that not apply to Japan - France imports ?

 

[Frenchastro]

Yes this applies (VAT 20, Import 4,2...) and yes the Price is all included.

They were knew when my friend bought them, but it turned out that they are not suitable for him, so technically speaking, I bought these eyepieces from the second hand market, with a price fixed freely between two people 😉...

''We still have this freedom to be able to freely buy the desired quantity of any product, to be mistaken about our choice, to resell it to whoever we want, where we want, at the price we want'' - Article number 1 of the Astronomical Trade Charter 😅

Edited August 2, 2023 by Frenchastro

[Louis D]

9 hours ago, Frenchastro said:

Yes this applies (VAT 20, Import 4,2...) and yes the Price is all included.

Does the seller collect VAT and remit it to the UK on international sales?  That's how sales tax works here in the US.  Sales between individuals, even internationally, don't have sales tax applied unless the seller has a sales tax permit and meets various other location and sales threshold requirements.  Technically, the buyer is supposed to remit use tax voluntarily when no sales tax is collected, but that rarely happens.  Direct international sales are only subject to federal duties, tariffs, and excise taxes when no marketplace is involved.

If you paid UK VAT, shouldn't your friend be able to get his Japan VAT refunded as a reseller?

[Frenchastro]

2 hours ago, Louis D said:

 

If you paid UK VAT, shouldn't your friend be able to get his Japan VAT refunded as a reseller?

That's where the problem is. My seller as a Japanese individual buyer in his country (not professional buyer or seller) paid the japanese VAT. Myself as a buyer I pay French VAT (I'm From France) and import taxes.

The same applies when I buy any item outside the European Union (on Astromart or ABS for example). And this even if my seller has already paid his vat in his country of residence. For example, when I was looking for a TSA102, one appeared for sale not far from London. It was much cheaper for me to take the eurostar between Paris and London,  go in the morning and return in the evening, rather than paying shipping and taxes.

In the present case, of course my japanese Friend sold me his Eyepieces at 1/3 of their purchase value. Because he's a friend, because he has used them, they were already unpacked, second hand sell between friends 😉