62 replies to this topic

[CrazyPanda]

Didn’t Al Nagler’s re-cooking of the std. Plossl recipe retool the TV models for improved serviceability down to f/4?

 

I have a 32 TVP, and owned two 20mm TVPs. I honestly don't/didn't see a noticeable improvement in edge of field performance over regular Plossls in these eyepieces at F/5.3, let alone any shorter. They're still just Plossls and have exactly the level of edge correction you'd expect of a Plossl in short focal ratios. If there *is* any advantage, it's certainly not significant.

Edited by CrazyPanda, 26 March 2025 - 04:04 PM.

[SeattleScott]

If one wants 85 AFOV for slow scopes and also want the central contrast in faster scopes, they can always just back off the eyepiece to cut off the outer field in faster scopes. Now at F5 you would have to back off a lot, and eye placement could become problematic. But it could help with using these eyepieces at F6-7 without as much distraction in the outer field. Especially with the models that have short ER anyway.

[Matthew Paul]

Masuyama DID, in the past, release some EPs having their optical secret sauce, yet stopped back to a 65* AFoV. When the FR of so many of the Japanese scopes is considered, f/9 & longer, Masuyama’s 85’s are suited quite nicely. It’s only the relatively new market phenomenon of hyper-fast FR’s for which their 85’s are lacking in outfield aberration suppression. 

 

In view of this, I wonder where the general Japanese scoping market & mindset are TODAY re: the hyper-fast FR phenom?

Very interesting!

I still found the edge correction to be lacking, in the f/7.7 TOA130b. It was OK in my F20 Dall-kirkham, but a Plossl looks like a Nagler at F/20.

 

I would not consider either of these scopes to be hyper-fast.

 

To me, they were best in that 68-72deg range. 

Edited by Matthew Paul, 27 March 2025 - 03:27 PM.

[Mike B]

Very interesting!

I still found the edge correction to be lacking, in the f/7.7 TOA130b. It was OK in my F20 Dall-kirkham, but a Plossl looks like a Nagler at F/20.

 

I would not consider either of these scopes to be hyper-fast.

 

To me, they were best in that 68-72deg range. 

Like the ol’ doctoring joke:

Patient:” Hey doc, it hurts when I do this!”

Doctor:” well, don’t DO that!” 

 

So with your Masuyama 85* EP, f it hurts your eyes to look beyond the 68-72* range- don't look out there!   Keep your gaze forward & on-axis. That’s the zone where these Eps excell so notably.

[Matthew Paul]

Like the ol’ doctoring joke:

Patient:” Hey doc, it hurts when I do this!”

Doctor:” well, don’t DO that!” 

 

So with your Masuyama 85* EP, f it hurts your eyes to look beyond the 68-72* range- don't look out there!   Keep your gaze forward & on-axis. That’s the zone where these Eps excell so notably.

It does not hurt to look out there.. The level of correction is non existent, making that part of the field essentially useless.

 

I can pull the field stop from a plossl and claim its an 72deg eyepiece that excels at on axis viewing, but its not really

Luckily these are priced well, and they do perform most excellently for 3/4 or more of their field, but I stand by my assessment that they should have been reduced to a 68-72deg eyepiece as this is the size of usable field. With their comfortable eye relief and the smaller field stop they would been a world class eyepiece with not a single fault to be found.  

I still use and like them, as they are great for a compact lightweight high transmission eyepiece with wonderful sharpness. They are just not really 85+ deg eyepieces and people should know that to make an informed decision. 

[SeattleScott]

It does not hurt to look out there.. The level of correction is non existent, making that part of the field essentially useless.

I can pull the field stop from a plossl and claim its an 72deg eyepiece that excels at on axis viewing, but its not really

Luckily these are priced well, and they do perform most excellently for 3/4 or more of their field, but I stand by my assessment that they should have been reduced to a 68-72deg eyepiece as this is the size of usable field. With their comfortable eye relief and the smaller field stop they would been a world class eyepiece with not a single fault to be found.

I still use and like them, as they are great for a compact lightweight high transmission eyepiece with wonderful sharpness. They are just not really 85+ deg eyepieces and people should know that to make an informed decision.

Good feedback.

One can always “make” them longer eye relief, 68-72 AFOV eyepieces by pulling back a bit from the eyepiece and cutting off the outer field. However, backing off too far could make eye placement tricky without adjustable height eyecup. Probably fine in the shorter focal lengths that don’t have much ER to begin with, but likely problematic in the longer focal lengths.

[doug mc]

 

While we are talking about eyepieces made in Japan, I am wondering if anyone knows who made this eyepiece. 84 degree 20mm. 

Attached Thumbnails

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Edited by doug mc, 27 March 2025 - 08:40 PM.

[starcanoe]

My favorite Masuyama? Oh, that's a tough one. I love all of them. I only have the 85° ones - yet - but I love them all. I only got the 32mm and 20mm a few weeks ago, but they became instant favorites.

 

In my first description of them to a friend, who was very curious about them, I described the 32mm as one of the finest eyepieces I've seen, and that the views were amazing, but while the 32mm was superb, the 20mm is pure magic. It's almost impossible to describe. The 20mm is perhaps the highest contrast eyepiece of all time. Certainly the best I've personally seen. And it is comfortable in an almost equally impossible way to describe. You feel like you just want to crawl into the eyepiece and live there. The view feels close, alive and engaging in a way lesser eyepieces can't even begin to touch. 

 

The 26mm, 16mm and 10mm are also amazing. In a recent observation of NGC 4449 with my 6" f/8 Dobsonian, I changed from an 11mm ES82 (in itself a very nice eyepiece) to the 10mm Masuyama 85° and was utterly shocked to find that the view in the 10/85 was brighter than in the 11mm ES82, despite the noticeably higher magnification. I could resolve the core and several knots and HII regions in the galaxy, which came as a complete surprise.

 

My biggest regret is not getting these eyepieces ten years ago. 

 

 

Clear skies!

Thomas, Denmark

 

Thats really saying something coming from you as I seem to recall you are a fairly serious and active observer. What f ratios are you using these eyepieces with BTW?

[Mike B]

 

While we are talking about eyepieces made in Japan, I am wondering if anyone knows who made this eyepiece. 84 degree 20mm. 

Here ya go!

[salishstars]

That was a fun article,  thank you Mike!

[Mike B]

It does not hurt to look out there.. The level of correction is non existent, making that part of the field essentially useless.

 

I can pull the field stop from a plossl and claim its an 72deg eyepiece that excels at on axis viewing, but its not really

Luckily these are priced well, and they do perform most excellently for 3/4 or more of their field, but I stand by my assessment that they should have been reduced to a 68-72deg eyepiece as this is the size of usable field. With their comfortable eye relief and the smaller field stop they would been a world class eyepiece with not a single fault to be found.  

I still use and like them, as they are great for a compact lightweight high transmission eyepiece with wonderful sharpness. They are just not really 85+ deg eyepieces and people should know that to make an informed decision. 

I’ve used poorly designed widefields for which the harshness of your “non-existent correction” appraisal is suitable… where outfield stars are stretched into bananas, seagulls, etc. These Masuyama’s are definitely NOT THAT! Nor should they suffer such inaccurate characterizations! Stars in their outfield extremities are still obviously stars and not at all useless, but entirely useFUL for general field & target orientation. No flying fruit salad here!

 

As to why their designer, Mr. Masuyama decided to fieldstop these at 85*… I am not knowing! Nor am I troubled by it. Like you, I enjoy them very much for what they are, as you’ve described perfectly!  

 

Your description here seems very fitting to their line of 53* EPs.

[Astrojensen]

Thats really saying something coming from you as I seem to recall you are a fairly serious and active observer. What f ratios are you using these eyepieces with BTW?

f/8 to f/15, chiefly. 

 

I've used the 26, 16 and 10 on my 125/1000mm Vixen catadioptric Newtonian with excellent results, and the 16 and 10 on my 6" f/8 Dobsonian with similar results. The edges aren't crisp, but they're not total disasters, either, and still eminently useful for target location and general context. The inner 50% of the field is essentially ortho-like sharpness and contrast, with the added benefit of the 85° field for context.  

 

In my 63/840mm (f/13.3) Zeiss Telemator, the entire field in the 32mm appears sharp, when you look at objects close to the center, because the lower resolution of the periphery of your vision doesn't allow you to detect the mild unsharpness of the stars. Even with direct vision, stars near the edge are only mildly bloated. Rich star fields and open clusters, such as the Double Cluster, or the area around M35, look amazing.  

 

It must be remembered, that these eyepieces are designed with slow f-ratios in mind, and to deliver the absolute maximum sharpness and contrast in such telescopes. They're not for fast systems under f/8. Even so, I've tested the 16mm in my 72mm f/6, with surprisingly decent results. The inner 50% of the field was still extremely sharp, while the edges were noticeably bloated, but less than I had anticipated. 

 

What I particularly like about them, is their small form factor, and low weight. This is very important for small telescopes. 

 

 

Clear skies!

Thomas, Denmark

[Matthew Paul]

I’ve used poorly designed widefields for which the harshness of your “non-existent correction” appraisal is suitable… where outfield stars are stretched into bananas, seagulls, etc. These Masuyama’s are definitely NOT THAT! Nor should they suffer such inaccurate characterizations! Stars in their outfield extremities are still obviously stars and not at all useless, but entirely useFUL for general field & target orientation. No flying fruit salad here!

This is 100% contrary to my experience.

It is THAT and my statement is not an inaccurate characterization. This echos what Astrojensen has stated as well.
 

That said, at the price point, and considering its other benefits, it's still a wonderful eyepiece design with all the traits that I previously mentioned. But it is NOT a fully corrected 85deg field of view and the outer stars of the field look a mess compared to what is seen at the center, even with a world class scope like the Takahashi TOA130b. 

 

I've used these eyepieces in F8 newtonians, F5 newtonians, F8 refractors, F20 Dall-Kirkham -- several of them being handmade award winning optics.

I'll reiterate, this is not to say that they are a bad eyepiece by any means and it is still a very valuable purchase given the quality of view in the central are that is well corrected. They are simply not corrected for the full 85deg field that they are advertised to provide. That's all that I'm saying. 

 

As I previously said, enlarging the field stop on a Plossl and claiming it's a 70deg eyepiece does not really make it a 70deg eyepiece, does it? 

This is not an emotional take or anything personal. The eyepiece is not well corrected in the outer field. This is a fact. I am sharing my experience of this factual statement with others so that they too are aware and not expecting a fully corrected field of view. 

• An explore scientific 82degree far exceeds the edge correction of this Masuyama series.
• A Nagler blows it out of the water for edge correction.

In my F20 Dall-Kirkham, a plossl looks like nagler level correction. These 85deg eyepieces outer field looks good in that scope, but not so in the F7.7 Takahashi refractor, or other scope that I've used them with. 

[balcon3]

This is 100% contrary to my experience.

It is THAT and my statement is not an inaccurate characterization. This echos what Astrojensen has stated as well.
 

That said, at the price point, and considering its other benefits, it's still a wonderful eyepiece design with all the traits that I previously mentioned. But it is NOT a fully corrected 85deg field of view and the outer stars of the field look a mess compared to what is seen at the center, even with a world class scope like the Takahashi TOA130b. 

 

I've used these eyepieces in F8 newtonians, F5 newtonians, F8 refractors, F20 Dall-Kirkham -- several of them being handmade award winning optics.

I'll reiterate, this is not to say that they are a bad eyepiece by any means and it is still a very valuable purchase given the quality of view in the central are that is well corrected. They are simply not corrected for the full 85deg field that they are advertised to provide. That's all that I'm saying. 

 

As I previously said, enlarging the field stop on a Plossl and claiming it's a 70deg eyepiece does not really make it a 70deg eyepiece, does it? 

This is not an emotional take or anything personal. The eyepiece is not well corrected in the outer field. This is a fact. I am sharing my experience of this factual statement with others so that they too are aware and not expecting a fully corrected field of view. 

• An explore scientific 82degree far exceeds the edge correction of this Masuyama series.
• A Nagler blows it out of the water for edge correction.

In my F20 Dall-Kirkham, a plossl looks like nagler level correction. These 85deg eyepieces outer field looks good in that scope, but not so in the F7.7 Takahashi refractor, or other scope that I've used them with. 

I have Masuyama 10/85 and 16/85 as well as Morpheus 9 and 12.5. I like them all, for different reasons. In my Tak FC100DF f7.4 refractor the Morpheus certainly puts up a much better corrected field right up to the edge. It's really nice, and it's almost as wide as the Masuyama (78 vs 85 degrees). But here's the thing. There is a price. Stars in the Morpheus are less brilliant, even in the center. In an open cluster, I see more faint stars with the Masuyamas and they really pop. When I go back and check with the Morpheus, I see that all the stars I saw in the Masyumas are actually visible in the Morpheus. But I had missed them at first because they did not stand out as well above the background. Thus the Masuyamas have more contrast. Stars also have richer colors across the spectrum in the Masuyamas. I find that I use both sets of eyepieces and I enjoy them in different ways. The Masuyamas get me to focus on the objects that are in the center of the field. The Morpheus's are nice for scanning because I can see the whole field sharply at once and there is something pleasing about that. But when I see something interesting in the Morpheus, I usually reach for the Masuyamas because I know I will see more detail on any particular object. 

[starcanoe]

These 85 degree Masuyamas reminds me of couple of ideas I've been mulling over for a year or two and have considered even starting a thread about it a time or two. First is designing a telescope that is optimized to provide the maximum contrast and resolution of a view of the moon...in particular the whole moon at once. A nearly color free well baffled refactor with good glass and impeccable polish is probably the main contender. And given that I'd want this to be a homemade scope and not a lot of money to throw at it...the first answer is a something like a 4 to 6 inch f30 ish or above achromatic refractor.  For something like that you kinda need a 2 inch (or slightly greater) field stop eyepiece. But you don't want the moon filling up the whole field of view! And you'd kinda like the AFOV to be on the wider side.

 

Pondering this it occurred to me that if operating at such high f ratios it would be possible to use pretty simple eyepiece designs that an ATM could make...either making some or all the lens themselves or purchasing lenses from optical companies. Something like a Ramsdens, Huygens, Kellner or my favorite design ATM design...a Clarke (in one of the ATM mags and can be found with a patent search).

 

Those work quite well at such slow f ratios....the workable apparent field of view is still only 50 ish degrees....but the aberrations REALLY blow up past that (or the eyepieces field curvature gets you). But it occurred to me. When you are looking at the moon....the stars around the moon really don't matter much (heck...most of them are blown out by all the light).

 

So, you can take the eyepieces above....keep the moon's disk in the 40 to 50 degree ish part of the field....and all that extra AFOV is just for framing the moon in the sky....you are going to see little to nothing there  anyway when looking at the moon.

 

 

The 85 degree  Masuyama's do that. And apparently the contrast/quality in the center part of the field of view is the cats meow. So, if you aren't trying to ATM the whole thing...you design/build a refactor that works with say the 20mm, 26mm or 32 mm 85 degree eyepieces. A 4 inch f20 refractor would be nearly color free and would match nicely with the 26mm. That Altair? 4 inch F11 with the EDish glass would match nicely with the 16 to 20mm.

 

Just some thoughts.

 

Oh this line of thinking would also apply to solar viewing. And viewing the planets at high power and just wanting them framed in a more immersive fashion.
 

Edited by starcanoe, 28 March 2025 - 11:46 AM.

[balcon3]

These 85 degree Masuyamas reminds me of couple of ideas I've been mulling over for a year or two and have considered even starting a thread about it a time or two. First is designing a telescope that is optimized to provide the maximum contrast and resolution of a view of the moon...in particular the whole moon at once. A nearly color free well baffled refactor with good glass and impeccable polish is probably the main contender. And given that I'd want this to be a homemade scope and not a lot of money to throw at it...the first answer is a something like a 4 to 6 inch f30 ish or above achromatic refractor.  For something like that you kinda need a 2 inch (or slightly greater) field stop eyepiece. But you don't want the moon filling up the whole field of view! And you'd kinda like the AFOV to be on the wider side.

 

Pondering this it occurred to me that if operating at such high f ratios it would be possible to use pretty simple eyepiece designs that an ATM could make...either making some or all the lens themselves or purchasing lenses from optical companies. Something like a Ramsdens, Huygens, Kellner or my favorite design ATM design...a Clarke (in one of the ATM mags and can be found with a patent search).

 

Those work quite well at such slow f ratios....the workable apparent field of view is still only 50 ish degrees....but the aberrations REALLY blow up past that (or the eyepieces field curvature gets you). But it occurred to me. When you are looking at the moon....the stars around the moon really don't matter much (heck...most of them are blown out by all the light).

 

So, you can take the eyepieces above....keep the moon's disk in the 40 to 50 degree ish part of the field....and all that extra AFOV is just for framing the moon in the sky....you are going to see little to nothing there  anyway when looking at the moon.

 

 

The 85 degree  Masuyama's do that. And apparently the contrast/quality in the center part of the field of view is the cats meow. So, if you aren't trying to ATM the whole thing...you design/build a refactor that works with say the 20mm, 26mm or 32 mm 85 degree eyepieces. A 4 inch f20 refractor would be nearly color free and would match nicely with the 26mm. That Altair? 4 inch F11 with the EDish glass would match nicely with the 16 to 20mm.

 

Just some thoughts.

 

Oh this line of thinking would also apply to solar viewing. And viewing the planets at high power and just wanting them framed in a more immersive fashion.
 

I think that the Masuyama 85s would work great with your idea. At a recent outreach event, I had my f7.4 Apo refractor set up with the Masuyama 26mm. That's only 28x and the moon filled only about 1/6 of the field. But people were mesmerized by the view. Much more so than with the Morpheus 12.5mm where the moon takes up about 1/3 of the field of view. The Masuyama put up a very high contrast view; the moon seemed 3D, suspended in black space.

[Mike B]

This is 100% contrary to my experience.

It is THAT and my statement is not an inaccurate characterization. This echos what Astrojensen has stated as well.
 

That said, at the price point, and considering its other benefits, it's still a wonderful eyepiece design with all the traits that I previously mentioned. But it is NOT a fully corrected 85deg field of view and the outer stars of the field look a mess compared to what is seen at the center, even with a world class scope like the Takahashi TOA130b. 

 

I've used these eyepieces in F8 newtonians, F5 newtonians, F8 refractors, F20 Dall-Kirkham -- several of them being handmade award winning optics.

I'll reiterate, this is not to say that they are a bad eyepiece by any means and it is still a very valuable purchase given the quality of view in the central are that is well corrected. They are simply not corrected for the full 85deg field that they are advertised to provide. That's all that I'm saying. 

 

As I previously said, enlarging the field stop on a Plossl and claiming it's a 70deg eyepiece does not really make it a 70deg eyepiece, does it? 

This is not an emotional take or anything personal. The eyepiece is not well corrected in the outer field. This is a fact. I am sharing my experience of this factual statement with others so that they too are aware and not expecting a fully corrected field of view. 

• An explore scientific 82degree far exceeds the edge correction of this Masuyama series.
• A Nagler blows it out of the water for edge correction.

In my F20 Dall-Kirkham, a plossl looks like nagler level correction. These 85deg eyepieces outer field looks good in that scope, but not so in the F7.7 Takahashi refractor, or other scope that I've used them with. 

My guess is that it’s FC we’re all seeing in these Masu-85’s where utilized in faster scopes. So it’s not an astigmatic issue of poor design or build quality, but merely a FR-limitation of the design. As Thomas attests:

 

In my 63/840mm (f/13.3) Zeiss Telemator, the entire field in the 32mm appears sharp….

Or Masuyama could stack a whole buncha extra glass in their 85’s to help their edge-performance be more like a conventional 82* EP…. But then they wouldn’t any longer be a 5-element Zeiss design.
 

If I load 500# of sack concrete in my Mazda Miata, I can hardly blame the Mazda design team for the car’s poor road performance therewith! Perhaps Mazda should put warning labels on their Miata vehicles about maximum payload limitations?

Likewise, Ford F-150 pickups should be clearly labeled for their slalom limitations, so that their operators should not push the G’s on the skid pad- especially when loaded with sack concrete!

 

Every CN thread I’ve seen on the Masu-85’s mentions their outfield performance limitations. Seems to me to be a sufficient headzup to any prospective EP buyers.

 

Thank-you Mr. Paul for your astute observations.

[Mike B]

Reading DonP’s OP description of EP aberrations I’m even more convinced of his description in #3 Field Curvature as being what we’re all seeing in these Masu-85 EPs “interaction” with fast scope optics! Just to satisfy my curiosity on this, on my next f/6 scope outing I’ll see how much of the outfield blur is a defocus thing, ameliorated by adjusting focus.

 

As I described previously, my commonly seen experience with poorly designed EP optics in a lesser widefield EP where outfield stars were aberrated into bananas & seagulls- this sounds like severe astigmatism, possibly compounded by FC and even coma if a reflecting scope is involved. This is very definitely NOT what my eye is seeing in these Masu-85 EPs! I’m seeing what I believe is the defocus blur of FC of the EP- worsened by the FC of the f/6 frac’s curved focal plane. This being the case, both optical ends of this scenario are simply behaving according to their design specs & the laws of optics. It’s not so much a matter of “poor correction” as it is of my “poor application” of these fine optical tools.

 

[starcanoe]

Good point Mike B

[Matthew Paul]

My guess is that it’s FC we’re all seeing in these Masu-85’s where utilized in faster scopes. So it’s not an astigmatic issue of poor design or build quality, but merely a FR-limitation of the design. As Thomas attests:

Or Masuyama could stack a whole buncha extra glass in their 85’s to help their edge-performance be more like a conventional 82* EP…. But then they wouldn’t any longer be a 5-element Zeiss design.
 

If I load 500# of sack concrete in my Mazda Miata, I can hardly blame the Mazda design team for the car’s poor road performance therewith! Perhaps Mazda should put warning labels on their Miata vehicles about maximum payload limitations?

Likewise, Ford F-150 pickups should be clearly labeled for their slalom limitations, so that their operators should not push the G’s on the skid pad- especially when loaded with sack concrete!

 

Every CN thread I’ve seen on the Masu-85’s mentions their outfield performance limitations. Seems to me to be a sufficient headzup to any prospective EP buyers.

 

Thank-you Mr. Paul for your astute observations.

I would think that too, however the Explore scientific and Televue eyepieces show wonderful edge corrections. . 

Mazda does not advertise a 500# sack of concrete performance handling though  

But, like we said, they are still great EPs

[Mike B]

I would think that too, however the Explore scientific and Televue eyepieces show wonderful edge corrections. . 

Mazda does not advertise a 500# sack of concrete performance handling though  

But, like we said, they are still great EPs

ES & TV wides definitely have their place- in the market and in focusers everywhere! However, no one is accusing them of being minimal-glass EPs 

 

And even my misguided misappropriation & misapplication of Masuyama’s 85* 5-el EPs in my f/6 frac reveals to my eye that there’s something displayed here not seen with the same splendour in my heavy glass-stack brand-X widefields!  

 

And come to think of it, Ford doesn’t list its truck’s skidpad performance in its advertising literature, either. Funny that!  
Altho, I DO recall many years ago a Road & Track field report on the road performance of a RoseParade float vehicle- the staff were somewhat dismayed at the vehicle’s abject failure in the slaloms, and that “the inside wheels lifted off the pavement during spirited cornering!” Plus they needed a calendar to time the vehicle in its 0-to-60 acceleration runs!

[Highburymark]

These 85 degree Masuyamas reminds me of couple of ideas I've been mulling over for a year or two and have considered even starting a thread about it a time or two. First is designing a telescope that is optimized to provide the maximum contrast and resolution of a view of the moon...in particular the whole moon at once. A nearly color free well baffled refactor with good glass and impeccable polish is probably the main contender. And given that I'd want this to be a homemade scope and not a lot of money to throw at it...the first answer is a something like a 4 to 6 inch f30 ish or above achromatic refractor. For something like that you kinda need a 2 inch (or slightly greater) field stop eyepiece. But you don't want the moon filling up the whole field of view! And you'd kinda like the AFOV to be on the wider side.

Pondering this it occurred to me that if operating at such high f ratios it would be possible to use pretty simple eyepiece designs that an ATM could make...either making some or all the lens themselves or purchasing lenses from optical companies. Something like a Ramsdens, Huygens, Kellner or my favorite design ATM design...a Clarke (in one of the ATM mags and can be found with a patent search).

Those work quite well at such slow f ratios....the workable apparent field of view is still only 50 ish degrees....but the aberrations REALLY blow up past that (or the eyepieces field curvature gets you). But it occurred to me. When you are looking at the moon....the stars around the moon really don't matter much (heck...most of them are blown out by all the light).

So, you can take the eyepieces above....keep the moon's disk in the 40 to 50 degree ish part of the field....and all that extra AFOV is just for framing the moon in the sky....you are going to see little to nothing there anyway when looking at the moon.


The 85 degree Masuyama's do that. And apparently the contrast/quality in the center part of the field of view is the cats meow. So, if you aren't trying to ATM the whole thing...you design/build a refactor that works with say the 20mm, 26mm or 32 mm 85 degree eyepieces. A 4 inch f20 refractor would be nearly color free and would match nicely with the 26mm. That Altair? 4 inch F11 with the EDish glass would match nicely with the 16 to 20mm.

Just some thoughts.

Oh this line of thinking would also apply to solar viewing. And viewing the planets at high power and just wanting them framed in a more immersive fashion.

Without wanting to deflect from the thread too much, this idea also appealed to me for solar Ha. Although I normally observe the Sun with minimum glass eyepieces, I have a pair of Nagler 13s which, together with a Maxbright II binoviewer, are just wide enough to fit the entire solar disc in the FOV at around 130x. It’s a spectacular view at such a high power, and equally spectacular on the Moon.
Back to the Masuyamas - a very interesting thread.

[Highburymark]

I have a 32 TVP, and owned two 20mm TVPs. I honestly don't/didn't see a noticeable improvement in edge of field performance over regular Plossls in these eyepieces at F/5.3, let alone any shorter. They're still just Plossls and have exactly the level of edge correction you'd expect of a Plossl in short focal ratios. If there *is* any advantage, it's certainly not significant.

Agree - ‘corrected down to F/4’ is a myth with TV Plossls, much as I love them otherwise.

[starcanoe]

Agree - ‘corrected down to F/4’ is a myth with TV Plossls, much as I love them otherwise.

 

I seem to recall that "corrected" down to F4 was more about the ON axis and sorta on axis abberations and color correction levels being a bit better than you run of the mill plossl at the time....which is bit different than claiming a major improvement in EDGE correction.

[ABQJeff]

I have only one Masuyama, the 50mm/53 degree. So by default it is my favorite Masuyama. BUT it is also one on my favorite long focal length eyepieces of my whole collection.

In my C11 Edge operating at F/7, the Masuymama provides excellent max exit pupil views with crisp stars to the edge. It gives me the best Rosette Nebula view of all my long FL eyepieces (Pentax 40XW, ES40-68, ES30-82, ES25-100, AT20-100XWA).

I have the 16/85 on my wish list for planetary binoviewing at F/17-F/26.

Edited by ABQJeff, 29 March 2025 - 05:37 PM.