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Masuyama or Ploessl

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#1 ThomasM

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Posted 10 November 2019 - 05:01 AM

The  new masuyama eyepieces (32,  26, 16  mm)   offer with 85 degree a  very large field of view in a rather compact housing for the price of poor edge sharpness.

 

But how do the sharpness compare with  the inner 50 degreee to that of a ploessl eyepiece with the same focal length? 



#2 havasman

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Posted 10 November 2019 - 05:36 AM

At what focal ratio?



#3 ThomasM

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Posted 10 November 2019 - 05:42 AM

At what focal ratio?

Very good point, I am most interested at f/5.5 to f/7. But, couldn't it be that the answer is almost independent of the focal ratio, because the sharpness degrades in both eyepieces with fast f ratio?

 

Thomas



#4 havasman

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Posted 10 November 2019 - 05:50 AM

Maybe so. But neither is generally recommended at those ratios. Both are going to be pretty well compromised. I have not used a Masuyama and have not used a Plossl since trying a couple years ago at f4.7.

 

My scopes' focal ratios are f4.49, f4.7, f5.4 and f7. Two are Newts and 2 refractors.



#5 jaraxx

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Posted 10 November 2019 - 07:27 AM

I have no experience with the Masuyama. I do have experience with Plossls, and if you're willing to constrain yourself to 50° and stick your eye right down to the glass the sharpness of a good Plossl is hard to beat. 



#6 Astrojensen

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Posted 10 November 2019 - 07:37 AM

Very good point, I am most interested at f/5.5 to f/7. But, couldn't it be that the answer is almost independent of the focal ratio, because the sharpness degrades in both eyepieces with fast f ratio?

 

Thomas

I *suspect* that the experience will be rather similar to erfles vs. plössls, IE the inner 50° are fine at f/6, but outside of that it starts to become progressively worse and at the edge, it's seagull heaven in newtonians and out of focus and blurred in short-ish refractors. 

 

 

Clear skies!
Thomas, Denmark



#7 ThomasM

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Posted 10 November 2019 - 10:52 AM

I *suspect* that the experience will be rather similar to erfles vs. plössls, IE the inner 50° are fine at f/6, but outside of that it starts to become progressively worse and at the edge, it's seagull heaven in newtonians and out of focus and blurred in short-ish refractors. 

 

 

Clear skies!
Thomas, Denmark

So you suspect that the Masuyamas are Erfle Eyepieces? I would also expect that the correction also depends on the glass type.



#8 Astrojensen

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Posted 10 November 2019 - 11:42 AM

So you suspect that the Masuyamas are Erfle Eyepieces? I would also expect that the correction also depends on the glass type.

No, just that the *experience* might be similar, not identical. I do know for a fact, that they are five-element eyepieces. The 50° Masuyamas were a redesign of the Zeiss Astroplan eyepiece (as were the Takahashi LEs, but they're apparently not identical), which in turn were a mix between an Erfle and a Plössl. 

 

Glass types play a critical role, obviously, but there's only so much you can do with five elements, if you also want an 85° AFOV. 

 

 

Clear skies!
Thomas, Denmark 


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#9 rowdy388

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Posted 10 November 2019 - 04:29 PM

Again, I only own one of the eyepieces being asked about: the 32mm Masuyama 85. 

I haven't owned a plossl in over a decade. The glass, polish, and coatings of the Masuyama

are premium. Only the best of the plossls probably match it in 50 degrees and then I'm still

thinking it's 5 lens against 4. The Masuyama should have the advantage. I use the 32 Masu

with a nebula filter (the best eyepiece for that purpose I've ever had) and don't require the

outer field to be great. For that I use the 31 Nagler.


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