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Eyepiece Musings: Transmission Values

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#26 RLK1

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Posted 05 June 2020 - 11:57 AM

Why would you give any credence to a “review” that contains that first sentence above? Again...Ludes used info for transmission rates that was scientifically measured by a firm that actually gets paid for doing such things. The Type 6 Naglers were shown by the interfometer to have transmission rates in the high 90’s. 

The first sentence regarding an observer's sentiments was in the quoted response from ThomasM who actually measured the transmission levels of Nagler T6 7&13mm eyepieces as noted in the CN thread referenced in my prior post. A response from Jon Isaacs above noted a 5mm was tested as well as a 13mm and no reference to a 7mm. Again, read the CN thread noted in my previous post...



#27 alnitak22

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Posted 05 June 2020 - 12:08 PM

The first sentence regarding an observer's sentiments was in the quoted response from ThomasM who actually measured the transmission levels of Nagler T6 7&13mm eyepieces as noted in the CN thread referenced in my prior post. A response from Jon Isaacs above noted a 5mm was tested as well as a 13mm and no reference to a 7mm. Again, read the CN thread noted in my previous post...

I know where the sentence comes from...it’s hardly scientific. More like juvenile. As for the T6 series, they have the same glass and coatings. To think one measure 10 higher or lower is rather absurd. But whatever.


Edited by alnitak22, 05 June 2020 - 12:10 PM.

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#28 Starman1

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Posted 05 June 2020 - 12:38 PM

Again, If anybody has any transmission values for the eyepieces in question in my initial post in this thread, please respond to it. ( I did see references to the 12.5mm UO Ortho so my thanks for the links relating to that one).
I understand there are other factors in play in what see can see thru an eyepiece, ie optical design, lens polish, lens configuration, optical-mechanical considerations and so forth.
I presume eyepiece manufacturers perform R&D on coatings for good reasons and with an ultimate goal of optimizing light transmission. Otherwise, they would not go through the time, effort and expense it takes to do so in the first place. With respect to the latter, I'm also skeptical of the some of the statements that you can't see the differences...

Someone may have measured the eyepieces you want measured but if so they haven't published the information.
As for seeing the difference, there have been lab studies done to show the minimum brightness difference detectable by the eye is 8 to 10%.
Also, the AAVSO says the minimum detectable difference in the visual reports they get is about 0.1 magnitude, or 10%.
So if we see differences in apparent transmission between eyepieces, and I think we do, the reasons are not likely to be due to a transmission difference unless that is only one factor of many that combine to make the difference.
One thing that brought that home to me was finding out I could see a lot more really faint stars when I added a Paracorr to the scope. I'm sure there is a 3% light loss, at least, when the Paracorr is added. But the faint moons of Uranus and faint stars in globular and even stars in M31 became visible that were not before.
2 factors were at work. One was the elimination of coma which blurred the really faint stars to extinction. The other was the slight increase in magnification, which, by darkening the background sky a tad, made fainter stars more visible.
So the slight loss of light, paradoxically, had the opposite effect than I expected. That was because factors other than the light loss were more important in determining what was visible when the percentage difference was so tiny.
Unless you compare exactly the same focal lengths you cannot ascribe any differences in visibility to transmission and even then other factors will be far more important.
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#29 MartinPond

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Posted 05 June 2020 - 12:44 PM

...

...

I had a good discussion here regarding a 40mm TV plossl. Yes, a 32MM generic gives pretty much the same FOV but with a little higher magnification. So why keep the 40mm?

 

Because it looks superior to my eye, that’s why. No calculation or lab analysis of AFOV, TFOV, or light transmission will convince me to sell it.

...

....

 

That was an awesome reminder:

 

Sometimes, one particular eyepiece is satisfying, even if you don't know why.

My grab-n-go kit has all "I'm satisfied and I don't know why" eyepieces.

I don't really know exactly how it is that this EP is so much 'better' than others, 

  even in the same series and type.  I guess at why this is the greatest.

   I just know I have to look at something through THIS EP, or I haven't

    experienced it fully.

 

Thanks for grounding the elaborate discussion.



#30 RLK1

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Posted 05 June 2020 - 12:50 PM

I know where the sentence comes from...it’s hardly scientific. More like juvenile. As for the T6 series, they have the same glass and coatings. To think one measure 10 higher or lower is rather absurd. But whatever.

From the reviewer in the CN eyepiece transmission thread:" Finally, the 'low' transmission of the Nagler 13 mm T6 was surprising, I got 87.6 % and now for a second Nagler 13 mm T6 I obtained 87.3 % ( compared to ~93% of the Nagler 9 mm T6 http://www.amateuras...ips/tips3.htm). I should add that the eyepiece was carefully cleaned, first with with a brush to removed dust, then with a microfaser fabric and 'optical wonder' cleaning agent from Baader."


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#31 RLK1

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Posted 05 June 2020 - 12:53 PM

Someone may have measured the eyepieces you want measured but if so they haven't published the information.
As for seeing the difference, there have been lab studies done to show the minimum brightness difference detectable by the eye is 8 to 10%.
Also, the AAVSO says the minimum detectable difference in the visual reports they get is about 0.1 magnitude, or 10%.
So if we see differences in apparent transmission between eyepieces, and I think we do, the reasons are not likely to be due to a transmission difference unless that is only one factor of many that combine to make the difference.
One thing that brought that home to me was finding out I could see a lot more really faint stars when I added a Paracorr to the scope. I'm sure there is a 3% light loss, at least, when the Paracorr is added. But the faint moons of Uranus and faint stars in globular and even stars in M31 became visible that were not before.
2 factors were at work. One was the elimination of coma which blurred the really faint stars to extinction. The other was the slight increase in magnification, which, by darkening the background sky a tad, made fainter stars more visible.
So the slight loss of light, paradoxically, had the opposite effect than I expected. That was because factors other than the light loss were more important in determining what was visible when the percentage difference was so tiny.
Unless you compare exactly the same focal lengths you cannot ascribe any differences in visibility to transmission and even then other factors will be far more important.

"Unless you compare exactly the same focal lengths you cannot ascribe any differences in visibility to transmission and even then other factors will be far more important."

Point well taken...


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#32 Eddgie

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Posted 05 June 2020 - 01:36 PM

I have owned two eyepeices out of the 70 or so I have owned over the years that in direct comparison to other eyepieces seemed dim.

 

One was a Meade 8.8mm Series 4000 Ultrawide (from the 1990s I believe).  One expert reviewer on CN said that this eyepiece had amazing transmission because the sky was blacker.  I agree that the sky was blacker, but I always wrote it up to the eyepiece being dimmer than most other eyepieces I had ever owned. This particular eyepiece was simply dim.

 

Later, I found one of the links where the transmission was tested for a similar Series 4000 UWA (6.7mm) and indeed, this eyepiece had transmission that was low enough in the blue and green end to make a difference and confirmed to me what I thought, which was that the reason the sky was blacker in this eyepiece was because the transmission was not as good as the other eyepieces I had at the time.

 

The second eyepiece was also a Meade S4000, but this time a plossl. during indoor comparisons, I noted that this eyepiece seemed slightly dimmer than similar focal lenght eyepieces. In addition, of all of the eyepeices I tested that day, this one stood out as less sharp than all of the others (and all of the others were too close to really see a difference, which made the Meade case particularly interesting because all others performed the same on modulation transfer test.

 

A very careful inspection of the eyepiece disclosed what I assumed was the problem.  The cementing between two of the elements was badly occluded with tiny bubbles and dust.  I could easily see this by using another eyepiece to peer down into the Plossl.  By moving the focal plane of the eyepiece closer or further away, I could actually see the cement.  It is not unusual for there to be small bubbles or inclusions in cement, but this particular eyepiece was extreme.

 

That's it.  In all of the eyepieces I have ever owned, only these two seemed to have enough transmission issue to be noticeable.  

 

I hope the OP gets the data he wants, but like others, I think that it would be extremely difficult to tell transmission differences between any good quality modern, fully mulitcoated eyepieces.  I have also come to believe that pretty much all modern good quality eyepieces have very high Strehl at the center of the field, and only differ significantly in their off axis performance. At the center of the field, the error is usually too small to be easily measured. 99.9% of the difference in performance is found when you move away from the center of the field.  How far you can go from the center and still have a diffraction limited image is the main difference in modern designs.  At the center of the field, all good quality eyepieces have a very high Strehl and will produce an image that is essentially perfect as compared to the telescope that forms the image.  


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#33 Jon Isaacs

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Posted 05 June 2020 - 02:44 PM

"When it comes to light throughput, they also suck. When comparing them to similar BGOs, I can easily see Rhea (Saturn's moon) with my EON 80 and the BGOs. With the Nagler type 6s, Rhea is not visible, even with averted vision.

"The transmission ot the nagler 7 and 13 mm T6 eyepieces is not top notch, I got values of 87%, almost 10% less transmission than that of Baader orthos in line with your findings.

Thomas"

CN thread: Eypiece transmission

Started by ThomasM, Nov 03 2012 06:47 PM

 

This is the actual link to that thread. 

 

https://www.cloudyni...e-transmission 

 

This is the actual link to Thomas's statement. 

 

https://www.cloudyni...-4#entry5329045

 

One thing to realize is that the tests were done at 532nm. These are Marcus's numbers for 

 

                                      450    500  550    600      650

TV Nagler 5mm Typ 6 90.79 91.83 95.24 96.86 94.11

TV Nagler 7mm Typ 6 90.37 91.34 94.27 96.33 94.69 

TV Nagler 9mm Typ 6 91.38 91.51 93.74 96.18 96.96 

 

Given the consistency of Markus's tests, for these 3 eyepieces, I am skeptical of the Thomas's M's results, as many were in that thread, something wasn't right.  

 

As a note:

It took me quite a while to find your quote. It shouldn't be that way.  It really requires a link.

 

From the TOS:

 

"A summary or short quote (one or two sentences) is acceptable without permission, but you must include the identity of the original source. The best way to direct fellow CN members to material you have found is to simply include a link, when possible, in your post."

 

https://www.cloudyni...tion=boardrules

 

Jon


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#34 alnitak22

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Posted 05 June 2020 - 03:05 PM

O

This is the actual link to that thread. 

 

https://www.cloudyni...e-transmission 

 

This is the actual link to Thomas's statement. 

 

https://www.cloudyni...-4#entry5329045

 

One thing to realize is that the tests were done at 532nm. These are Marcus's numbers for 

 

                                      450    500  550    600      650

TV Nagler 5mm Typ 6 90.79 91.83 95.24 96.86 94.11

TV Nagler 7mm Typ 6 90.37 91.34 94.27 96.33 94.69 

TV Nagler 9mm Typ 6 91.38 91.51 93.74 96.18 96.96 

 

Given the consistency of Markus's tests, for these 3 eyepieces, I am skeptical of the Thomas's M's results, as many were in that thread, something wasn't right.  

 

As a note:

It took me quite a while to find your quote. It shouldn't be that way.  It really requires a link.

 

From the TOS:

 

"A summary or short quote (one or two sentences) is acceptable without permission, but you must include the identity of the original source. The best way to direct fellow CN members to material you have found is to simply include a link, when possible, in your post."

 

https://www.cloudyni...tion=boardrules

 

Jon

Correct. And it bears repeating that the firm that Markus’ used for transmission data  was an optics company that does this kind of testing routinely, not an amateur astronomer. Who may or   may not be precise, or who may or may not have some personal feelings tied up in his results.



#35 RLK1

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Posted 05 June 2020 - 03:25 PM

This is the actual link to that thread. 

 

https://www.cloudyni...e-transmission 

 

This is the actual link to Thomas's statement. 

 

https://www.cloudyni...-4#entry5329045

 

One thing to realize is that the tests were done at 532nm. These are Marcus's numbers for 

 

                                      450    500  550    600      650

TV Nagler 5mm Typ 6 90.79 91.83 95.24 96.86 94.11

TV Nagler 7mm Typ 6 90.37 91.34 94.27 96.33 94.69 

TV Nagler 9mm Typ 6 91.38 91.51 93.74 96.18 96.96 

 

Given the consistency of Markus's tests, for these 3 eyepieces, I am skeptical of the Thomas's M's results, as many were in that thread, something wasn't right.  

 

As a note:

It took me quite a while to find your quote. It shouldn't be that way.  It really requires a link.

 

From the TOS:

 

"A summary or short quote (one or two sentences) is acceptable without permission, but you must include the identity of the original source. The best way to direct fellow CN members to material you have found is to simply include a link, when possible, in your post."

 

https://www.cloudyni...tion=boardrules

 

Jon

While I don't see a problem with Thomas testing at 532 nm and then repeating his testing on two different samples for reproducibility,  I noted in my initial post in this thread: "While I realize the values may not be specific to each iteration of ocular, I'm particularly interested in those above 95%..." Also noted in my initial post: "Expect to find some variation on the specifics of the tests employed by those making the determinations."  So, indeed, there are some variations, both in testing procedures as well as in finding on some iterations of the same oculars, as demonstrated by the various links supplied in this thread by other posters.

As far as the "rules" go, I'll keep them in mind for next time although I don't see any moderators getting their underwear in a twist because I happened to reference a prior CN thread instead of linking to it. In fact, I think researching and reviewing an entire thread instead of a link isn't a bad thing to do.

Generally speaking, I have nothing against T6 naglers other than when I tried a couple in my scope, they didn't give me the space walk/space portal type of viewing experience as compared to the two inch naglers I've experienced in the past. 

But, at the end of the day, and when I'm after something like this, I'll go with an eyepiece that I believe to be up to the task: "Uranus has two harder-to-see satellites that will really test your observing acumen. With a 16-inch telescope, an eyepiece that gives a magnification above 250x, and excellent viewing conditions, you just might glimpse the smaller satellites Ariel and Umbriel. Ariel glows at magnitude 13.2 but remains within 14" of Uranus (3.75 diameters). Magnitude 14.0 Umbriel never appears more than 20" from the planet (5.5 diameters). Use planetarium software to pinpoint their positions before you begin your search."

https://astronomy.co...-the-ice-giants

and:

https://www.universe...e-solar-system/

In regards to the above, I'd prefer to know the specifics of the eyepieces and have them in place and ready to go rather than doing a comparo in colder winter temperatures...



#36 Starman1

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Posted 05 June 2020 - 05:28 PM

While I don't see a problem with Thomas testing at 532 nm and then repeating his testing on two different samples for reproducibility,  I noted in my initial post in this thread: "While I realize the values may not be specific to each iteration of ocular, I'm particularly interested in those above 95%..." Also noted in my initial post: "Expect to find some variation on the specifics of the tests employed by those making the determinations."  So, indeed, there are some variations, both in testing procedures as well as in finding on some iterations of the same oculars, as demonstrated by the various links supplied in this thread by other posters.

As far as the "rules" go, I'll keep them in mind for next time although I don't see any moderators getting their underwear in a twist because I happened to reference a prior CN thread instead of linking to it. In fact, I think researching and reviewing an entire thread instead of a link isn't a bad thing to do.

Generally speaking, I have nothing against T6 naglers other than when I tried a couple in my scope, they didn't give me the space walk/space portal type of viewing experience as compared to the two inch naglers I've experienced in the past. 

But, at the end of the day, and when I'm after something like this, I'll go with an eyepiece that I believe to be up to the task: "Uranus has two harder-to-see satellites that will really test your observing acumen. With a 16-inch telescope, an eyepiece that gives a magnification above 250x, and excellent viewing conditions, you just might glimpse the smaller satellites Ariel and Umbriel. Ariel glows at magnitude 13.2 but remains within 14" of Uranus (3.75 diameters). Magnitude 14.0 Umbriel never appears more than 20" from the planet (5.5 diameters). Use planetarium software to pinpoint their positions before you begin your search."

https://astronomy.co...-the-ice-giants

and:

https://www.universe...e-solar-system/

In regards to the above, I'd prefer to know the specifics of the eyepieces and have them in place and ready to go rather than doing a comparo in colder winter temperatures...

Ariel and Umbriel are always visible with direct vision in my 12.5", usually at 400-500x.  Not at the limit at all.  Now, Miranda is very different.

That one is one tough cookie.--one possible averted vision glimpse out of over 20 tries.  But it's 2 magnitudes fainter and closer to Uranus.



#37 RLK1

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Posted 05 June 2020 - 05:52 PM

Ariel and Umbriel are always visible with direct vision in my 12.5", usually at 400-500x.  Not at the limit at all.  Now, Miranda is very different.

That one is one tough cookie.--one possible averted vision glimpse out of over 20 tries.  But it's 2 magnitudes fainter and closer to Uranus.

The minimum aperture for Miranda that I've seen referenced in my google search is 18"although that's likely for a direct, non-averted vision observation. 

If your seeing conditions typically allow for 400-500X then I'd certainly expect them (Ariel/Umbriel) to be "always visible" in your 12.5". 

While I've seen them before, it's been quite awhile, and I'd likely use a 6mm/9mm ortho to observe them in my 16".
 



#38 Allan Wade

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Posted 06 June 2020 - 09:32 PM

I don’t worry too much about the numbers, I just work out what’s what under the stars. How this has worked for me, is that I’ve built a lineup of eyepieces for maximum transmission. What I personally found, was that initially in my smaller scopes, I couldn’t really tell any difference between these and my widefields when looking at faint deep sky targets. 
 

But the plan came together when the 32” arrived, and now I see the difference quite obviously between my Delos and ZAO and Tak Abbe eyepieces. Despite a comment in one of the earlier posts, it’s almost never a case of seeing something through the min glass eyepieces and not seeing it in the Delos. Though that has happened once or twice. The real difference is toward the limit when I can hold an object in direct vision in the Abbe Orthos but only with averted vision in the Delos. That happens often, and I enjoy the benefit of being able to observe the target with direct vision. Then there are the situations where I can’t positively confirm an observation with the Delos, but it becomes certain in the min glass eyepieces, that happens a lot too.

 

So I certainly see great benefit in observing with maximum transmission eyepieces, but the strategy becomes more relevant as you slide up the aperture scale. 


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#39 Allan Wade

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Posted 06 June 2020 - 09:57 PM

The minimum aperture for Miranda that I've seen referenced in my google search is 18"although that's likely for a direct, non-averted vision observation. 

If your seeing conditions typically allow for 400-500X then I'd certainly expect them (Ariel/Umbriel) to be "always visible" in your 12.5". 

While I've seen them before, it's been quite awhile, and I'd likely use a 6mm/9mm ortho to observe them in my 16".
 

Titania, Ariel and Oberon are the 3 easy moons of Uranus to see. They reside in the high magnitude 13’s and are reasonably separated from the planet. They are easy pickings in a 12”. I haven’t tried for them in smaller scopes, but suspect an 8” under dark skies would see them.

 

I wouldn’t classify Umbriel as easy in a 12”. It’s a magnitude fainter and resides much closer to Uranus than Titania and Oberon. Don has good eyes though, so he might find Umbriel not too difficult. 
 

Miranda is very tough, with very few positive observations. It’s magnitude 16, but the real problem is it never strays further than 9” away from Uranus. I’ve had a few attempts with the 32” without success, and plan to give it a proper look this coming opposition.

 

Make the most of Mars this year as well. If you haven’t seen Deimos, I found that one without trouble from about three months out from opposition in a 12” and it’s a pretty easy observation around opposition. Phobos is more difficult, and best left right around opposition in my experience. Practice with those helps a lot when tackling the really hard stuff like Miranda.


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#40 JuergenB

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Posted 07 June 2020 - 11:36 AM

Some things to know:

--the curve of transmission is as important as its height.

If a transmission test doesn't measure at at least 5 wavelengths, it won't tell you much.

--a 10% difference only represents 0.1 magnitude.  That's less than the hour-to-hour change in the sky brightness.

And about the limit of human vision in a lab, not the field. 

After all, the typical reflector has a light loss of 30% at the edge of the field in a low power eyepiece, and we don't notice it.

I completely agree that peak transmission is less important than the transmission curve itself. A bit offt-topic because it is not about eyepieces but whole binoculars: Last summer we rented a pair of Pentax 8x42 DCF binoculars at ATHOS star camp on La Palma island. The views could have been beautiful but I immediately was distracted by the lack of truly red stars. Everything was shifted to the blue, even Antares looked very pale.

 

After being back home, I found an interesting website with reviews and comparisons of a broad selection of binoculars, http://www.allbinos.com/. They had tested not exactly the same bino, but a Pentax SD 9x42 WP: https://www.allbinos...SD_9x42_WP.html. The published transmission curve and the comments were somewhat shocking - but they gave an exact explanation about why the red stars were so dim. I guess that the coatings of both binos are similar.

 

It is difficult to tell apart the contribution of the objectives, the prisms and the eyepieces to the transmission curve but certainly the eyepieces play a role in color rendition.

 

I always prefer a neutral color rendition over warm or cold hues, be it for planets or for stars.

 

Juergen



#41 Starman1

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Posted 07 June 2020 - 12:10 PM

I completely agree that peak transmission is less important than the transmission curve itself. A bit offt-topic because it is not about eyepieces but whole binoculars: Last summer we rented a pair of Pentax 8x42 DCF binoculars at ATHOS star camp on La Palma island. The views could have been beautiful but I immediately was distracted by the lack of truly red stars. Everything was shifted to the blue, even Antares looked very pale.

 

After being back home, I found an interesting website with reviews and comparisons of a broad selection of binoculars, http://www.allbinos.com/. They had tested not exactly the same bino, but a Pentax SD 9x42 WP: https://www.allbinos...SD_9x42_WP.html. The published transmission curve and the comments were somewhat shocking - but they gave an exact explanation about why the red stars were so dim. I guess that the coatings of both binos are similar.

 

It is difficult to tell apart the contribution of the objectives, the prisms and the eyepieces to the transmission curve but certainly the eyepieces play a role in color rendition.

 

I always prefer a neutral color rendition over warm or cold hues, be it for planets or for stars.

 

Juergen

A slanted or peaked transmission-by-wavelength curve can yield odd results.

 

I am not one who particularly is sensitive to "tone" in eyepieces, so I figured out a way to see the differences easily.

Most eyepieces just seem "normal" after a minute of looking.

 

In the daytime, I have a white building a few miles away that is large enough I can see its color quite easily with my naked eye.

It also has a red windsock on the top that is easy to spot with no optical aid.  It can help reveal if red is over-prominent or subdued.

 

I aim the telescope at the building and insert an eyepiece.  Moving quickly from eyepiece to naked eye view and back again, very small tonal biases can be detected.

The most common tones I see in eyepieces are a yellowing of the white in the building.  I see this in many if not most eyepieces that use lanthanum oxide glass.

But I have also seen a bias toward the blue, and even one that was decidedly pink!  I'm not exactly sure what to think when I see (and it's in many eyepieces) the white of the building

become a light grey in the eyepiece.  Does this indicate a lower transmission overall?  If not, what does it say about the tonal character of the eyepiece?  I'm not sure.

It may simply be a darkening due to magnification, because not all the eyepieces I've tested this way have been low power eyepieces.

 

At any rate, unless the tonality is particularly egregious, I don't usually remark about it.

This test reveals if there is any chromatic aberration of the exit pupil as well, or simple chromatic smear in the outer field, merely by moving the white building back and forth in the field.

 

I used to sell binoculars, however, and the color tint variations in binoculars are much larger than those in telescope eyepieces.  So Juergen's finding is not unusual.


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#42 RLK1

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Posted 07 June 2020 - 12:16 PM

I completely agree that peak transmission is less important than the transmission curve itself. A bit offt-topic because it is not about eyepieces but whole binoculars: Last summer we rented a pair of Pentax 8x42 DCF binoculars at ATHOS star camp on La Palma island. The views could have been beautiful but I immediately was distracted by the lack of truly red stars. Everything was shifted to the blue, even Antares looked very pale.

 

After being back home, I found an interesting website with reviews and comparisons of a broad selection of binoculars, http://www.allbinos.com/. They had tested not exactly the same bino, but a Pentax SD 9x42 WP: https://www.allbinos...SD_9x42_WP.html. The published transmission curve and the comments were somewhat shocking - but they gave an exact explanation about why the red stars were so dim. I guess that the coatings of both binos are similar.

 

It is difficult to tell apart the contribution of the objectives, the prisms and the eyepieces to the transmission curve but certainly the eyepieces play a role in color rendition.

 

I always prefer a neutral color rendition over warm or cold hues, be it for planets or for stars.

 

Juergen

"I always prefer a neutral color rendition over warm or cold hues, be it for planets or for stars." 

So, just to be clear, you're talking about the tone of the eyepiece? Orthoscopics designs(not all, but most) are generally referred to as having cool or neutral tones and are my preference for planetary/ planetary moon(s) observations. I also believe overall light transmission of these oculars can be very valuable in DSOs as well. I tend to equate the neutral color rendition with a  "cool" tone eyepiece more so than with a "warm" tone eyepiece. I tend to prefer the so-called "clinical" view of the neutral/cool tone eyepieces in critical viewing sessions...



#43 JuergenB

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Posted 07 June 2020 - 01:17 PM

"I always prefer a neutral color rendition over warm or cold hues, be it for planets or for stars." 

So, just to be clear, you're talking about the tone of the eyepiece? Orthoscopics designs(not all, but most) are generally referred to as having cool or neutral tones and are my preference for planetary/ planetary moon(s) observations. I also believe overall light transmission of these oculars can be very valuable in DSOs as well. I tend to equate the neutral color rendition with a  "cool" tone eyepiece more so than with a "warm" tone eyepiece. I tend to prefer the so-called "clinical" view of the neutral/cool tone eyepieces in critical viewing sessions...

Yes, I am talking of a tone of the eyepiece, which depends on glass types, number of lenses and spectral charasteristics of the coating. I also like a "cool" rendering as long as it is not just a shift to the blue part of the spectrum like in those Pentax binoculars I had used. Regarding Pentax, never looked through their famous XW eyepieces, but I assume that their transmission characteristics are different from those binos.

 

For me it is important that I can judge the spectral classes of stars from the colors (for example, deciding between A, F and G types easily). With my TV Plössls on the TSA-120, this is not difficult. The same applies to my Zeiss 8x42 FL T* bino, which has a very good color rendition as well.

 

Juergen
 



#44 RLK1

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Posted 07 June 2020 - 01:47 PM

Yes, I am talking of a tone of the eyepiece, which depends on glass types, number of lenses and spectral charasteristics of the coating. I also like a "cool" rendering as long as it is not just a shift to the blue part of the spectrum like in those Pentax binoculars I had used. Regarding Pentax, never looked through their famous XW eyepieces, but I assume that their transmission characteristics are different from those binos.

 

For me it is important that I can judge the spectral classes of stars from the colors (for example, deciding between A, F and G types easily). With my TV Plössls on the TSA-120, this is not difficult. The same applies to my Zeiss 8x42 FL T* bino, which has a very good color rendition as well.

 

Juergen
 

Thanks for your reply. I note the TV plossls are reportedly "warm" in tone.




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