Author Topic: Masuyama on Binoscope  (Read 200 times)

noerivatat

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Re: Masuyama on Binoscope
« Reply #15 on: January 26, 2018, 08:12:01 AM »
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Thank you for the time taken to produce this report. While the Masu's shortcomings in relatively "fastish - medium" focal length scopes has been noted in other threads, I guess the elephant herd in the living room is the significant variance between declared and actual FOV!!!

So, do you feel it's worth holding on to the Masuyamas or for the times a large exit pupil is needed, a cheaper eyepiece would be sufficient (given that the 22 Nag is indeed an awesome eyepiece - be it in monocular or binocular viewing)?

Nagler is a better choice if you do not need that large exit pupil.
If you do need that large exit pupil and you have a relatively fast scope and you do not mind the smaller afov, Sky Rover ED 30(or its equilevant) is a better choice.
If you do need that large exit pupil and you have arelatively slow scope and you do want an extra wide afov, Masu may be the only way to go.
Overall, I consider a cheaper eyepiece would be sufficient.
Thanks a lot for your nice report, actually, I just got aware of your nice TBM apo binoscope, this is certainly an excellent instrument. I fully agree with your findings, but to some extend my conclusion is slightly different. I am using also a pair of 17 mm Ethos which I really like, so the Nagler 22 has almost the same true field of view (field stop diameter 31.1 mm versus 29.6 mm of the Ethos 17 mm). The Masuyama with its 47 mm field stop give much wider views, it is also much wider than the ED 30 (35 mm field stop?). Certainly, it is not perfect in the 30 % outer part, but I really like. My impression, it is the best in its class (large exit pupil AND maximum field of view) for binoviewing.

Thomas
My pleasure.
You are quite right in saying the Masuyama is unique and irreplaceable. No other oculars in production has similar characteristics.
But remember the Lzos lens are F6 and a bit too fast for this ocular.
One thing I do not find satisfactory except the edge : The afov is actually short of its specification. With a sub- 80° it's noticeably smaller than a Nagler, which I do not find immersive either.
I think I'll stick to the E17, they give me a 100° afov and 2.3° tfov which is very nice indeed. Though I strongly recommend the Masuyama to any binoscope with longer focal length or slower focal ratio, such as 120F7.5, 130F9, 140F7, 152F8, etc.

Jason Harlan

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Re: Masuyama on Binoscope
« Reply #16 on: January 30, 2018, 11:27:31 PM »
Quote
Quote

Thank you for the time taken to produce this report. While the Masu's shortcomings in relatively "fastish - medium" focal length scopes has been noted in other threads, I guess the elephant herd in the living room is the significant variance between declared and actual FOV!!!

So, do you feel it's worth holding on to the Masuyamas or for the times a large exit pupil is needed, a cheaper eyepiece would be sufficient (given that the 22 Nag is indeed an awesome eyepiece - be it in monocular or binocular viewing)?

Nagler is a better choice if you do not need that large exit pupil.
If you do need that large exit pupil and you have a relatively fast scope and you do not mind the smaller afov, Sky Rover ED 30(or its equilevant) is a better choice.
If you do need that large exit pupil and you have arelatively slow scope and you do want an extra wide afov, Masu may be the only way to go.
Overall, I consider a cheaper eyepiece would be sufficient.
Thanks a lot for your nice report, actually, I just got aware of your nice TBM apo binoscope, this is certainly an excellent instrument. I fully agree with your findings, but to some extend my conclusion is slightly different. I am using also a pair of 17 mm Ethos which I really like, so the Nagler 22 has almost the same true field of view (field stop diameter 31.1 mm versus 29.6 mm of the Ethos 17 mm). The Masuyama with its 47 mm field stop give much wider views, it is also much wider than the ED 30 (35 mm field stop?). Certainly, it is not perfect in the 30 % outer part, but I really like. My impression, it is the best in its class (large exit pupil AND maximum field of view) for binoviewing.

Thomas[/quote]
My pleasure.
You are quite right in saying the Masuyama is unique and irreplaceable. No other oculars in production has similar characteristics.
But remember the Lzos lens are F6 and a bit too fast for this ocular.
One thing I do not find satisfactory except the edge : The afov is actually short of its specification. With a sub- 80° it's noticeably smaller than a Nagler, which I do not find immersive either.
I think I'll stick to the E17, they give me a 100° afov and 2.3° tfov which is very nice indeed. Though I strongly recommend the Masuyama to any binoscope with longer focal length or slower focal ratio, such as 120F7.5, 130F9, 140F7, 152F8, etc.[/quote]
I see your point, the field of view specified for the Masyama is smaller than what you got.

On the other hand, I think some caution is needed when comparing the aparent field of view of super wide eyepieces. If you assume that the TFOV is given by the AFOV devided by the magnification, then the AFOV is only given by the field stop size and focal length and can be calculated by 360 degree x fields stop diameter/ focal length x2 pi, i.s 57.6 degree x field stop diameter/ focal length. Now you get 84.6 degree for the Masuyama 32 (47 mm field stop) which is pretty close to the specification of 85 degree, 81.4 degreee for the Nagler 22 (31. mm field stop) and 100,3 degree for the Ethos 17 mm (29.6 mm field stop). Now, in a strict sense for an eyepiece without any distorsion the AFOV can be calculated by 2x arctan ( field stop / 2x focal length) and now you get 72,5 degree for the Masyama 32, 70,5 degree for the Nagler 22 and 82 degree for the Ethos 17 mm, all numbers significantly smaller than specified (for a narrow angle eyepiece both numbers will be off course equal). Now the question, why did you got 81.3 degree for the Nagler 22 and 77 degree for the Masuyama 32? Both values are larger than expected but in a different way. Different distorsion?

My conclusion, I would not argue that the AFOV of the Masuyama 32 is less than specified, it is common practice to calculate the AFOV just from the field stop diameter. Moreover, at least my impression, the AFOV looks much wider than that of other wide angle eyepieces, e.g. Hyperion 36 mm with is specified with 72 degree.

Thomas

Jeremy Swaine

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Re: Masuyama on Binoscope
« Reply #17 on: January 31, 2018, 01:27:31 AM »
Quote
Quote

Thank you for the time taken to produce this report. While the Masu's shortcomings in relatively "fastish - medium" focal length scopes has been noted in other threads, I guess the elephant herd in the living room is the significant variance between declared and actual FOV!!!

So, do you feel it's worth holding on to the Masuyamas or for the times a large exit pupil is needed, a cheaper eyepiece would be sufficient (given that the 22 Nag is indeed an awesome eyepiece - be it in monocular or binocular viewing)?

Nagler is a better choice if you do not need that large exit pupil.
If you do need that large exit pupil and you have a relatively fast scope and you do not mind the smaller afov, Sky Rover ED 30(or its equilevant) is a better choice.
If you do need that large exit pupil and you have arelatively slow scope and you do want an extra wide afov, Masu may be the only way to go.
Overall, I consider a cheaper eyepiece would be sufficient.
Thanks a lot for your nice report, actually, I just got aware of your nice TBM apo binoscope, this is certainly an excellent instrument. I fully agree with your findings, but to some extend my conclusion is slightly different. I am using also a pair of 17 mm Ethos which I really like, so the Nagler 22 has almost the same true field of view (field stop diameter 31.1 mm versus 29.6 mm of the Ethos 17 mm). The Masuyama with its 47 mm field stop give much wider views, it is also much wider than the ED 30 (35 mm field stop?). Certainly, it is not perfect in the 30 % outer part, but I really like. My impression, it is the best in its class (large exit pupil AND maximum field of view) for binoviewing.

Thomas[/quote]
My pleasure.
You are quite right in saying the Masuyama is unique and irreplaceable. No other oculars in production has similar characteristics.
But remember the Lzos lens are F6 and a bit too fast for this ocular.
One thing I do not find satisfactory except the edge : The afov is actually short of its specification. With a sub- 80° it's noticeably smaller than a Nagler, which I do not find immersive either.
I think I'll stick to the E17, they give me a 100° afov and 2.3° tfov which is very nice indeed. Though I strongly recommend the Masuyama to any binoscope with longer focal length or slower focal ratio, such as 120F7.5, 130F9, 140F7, 152F8, etc.[/quote]
I see your point, the field of view specified for the Masyama is smaller than what you got.

On the other hand, I think some caution is needed when comparing the aparent field of view of super wide eyepieces. If you assume that the TFOV is given by the AFOV devided by the magnification, then the AFOV is only given by the field stop size and focal length and can be calculated by 360 degree x fields stop diameter/ focal length x2 pi, i.s 57.6 degree x field stop diameter/ focal length. Now you get 84.6 degree for the Masuyama 32 (47 mm field stop) which is pretty close to the specification of 85 degree, 81.4 degreee for the Nagler 22 (31. mm field stop) and 100,3 degree for the Ethos 17 mm (29.6 mm field stop). Now, in a strict sense for an eyepiece without any distorsion the AFOV can be calculated by 2x arctan ( field stop / 2x focal length) and now you get 72,5 degree for the Masyama 32, 70,5 degree for the Nagler 22 and 82 degree for the Ethos 17 mm, all numbers significantly smaller than specified (for a narrow angle eyepiece both numbers will be off course equal). Now the question, why did you got 81.3 degree for the Nagler 22 and 77 degree for the Masuyama 32? Both values are larger than expected but in a different way. Different distorsion?

My conclusion, I would not argue that the AFOV of the Masuyama 32 is less than specified, it is common practice to calculate the AFOV just from the field stop diameter. Moreover, at least my impression, the AFOV looks much wider than that of other wide angle eyepieces, e.g. Hyperion 36 mm with is specified with 72 degree.

Thomas[/quote]
I do not do any calculation.
I use the Leica asph 25-50x(75°@50x, which has been measured and confirmed many times) as a benchmark. You can use other confirmed benchmarks such as the Docter 12.5mm=84°.
Then I take a picutre behind the eyepiece and compare it to the Leica via diameter in pixels directly.
Both 81.3° and 77.1° are results comparing with Leica's 50x @75°.
There will be some errors in measurement but I think this is the most direct approach to ascertain an afov.

clicpostreta

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Re: Masuyama on Binoscope
« Reply #18 on: February 09, 2018, 08:29:53 AM »
Quote
Quote

Thank you for the time taken to produce this report. While the Masu's shortcomings in relatively "fastish - medium" focal length scopes has been noted in other threads, I guess the elephant herd in the living room is the significant variance between declared and actual FOV!!!

So, do you feel it's worth holding on to the Masuyamas or for the times a large exit pupil is needed, a cheaper eyepiece would be sufficient (given that the 22 Nag is indeed an awesome eyepiece - be it in monocular or binocular viewing)?

Nagler is a better choice if you do not need that large exit pupil.
If you do need that large exit pupil and you have a relatively fast scope and you do not mind the smaller afov, Sky Rover ED 30(or its equilevant) is a better choice.
If you do need that large exit pupil and you have arelatively slow scope and you do want an extra wide afov, Masu may be the only way to go.
Overall, I consider a cheaper eyepiece would be sufficient.
Thanks a lot for your nice report, actually, I just got aware of your nice TBM apo binoscope, this is certainly an excellent instrument. I fully agree with your findings, but to some extend my conclusion is slightly different. I am using also a pair of 17 mm Ethos which I really like, so the Nagler 22 has almost the same true field of view (field stop diameter 31.1 mm versus 29.6 mm of the Ethos 17 mm). The Masuyama with its 47 mm field stop give much wider views, it is also much wider than the ED 30 (35 mm field stop?). Certainly, it is not perfect in the 30 % outer part, but I really like. My impression, it is the best in its class (large exit pupil AND maximum field of view) for binoviewing.

Thomas[/quote]
My pleasure.
You are quite right in saying the Masuyama is unique and irreplaceable. No other oculars in production has similar characteristics.
But remember the Lzos lens are F6 and a bit too fast for this ocular.
One thing I do not find satisfactory except the edge : The afov is actually short of its specification. With a sub- 80° it's noticeably smaller than a Nagler, which I do not find immersive either.
I think I'll stick to the E17, they give me a 100° afov and 2.3° tfov which is very nice indeed. Though I strongly recommend the Masuyama to any binoscope with longer focal length or slower focal ratio, such as 120F7.5, 130F9, 140F7, 152F8, etc.[/quote]
I see your point, the field of view specified for the Masyama is smaller than what you got.

On the other hand, I think some caution is needed when comparing the aparent field of view of super wide eyepieces. If you assume that the TFOV is given by the AFOV devided by the magnification, then the AFOV is only given by the field stop size and focal length and can be calculated by 360 degree x fields stop diameter/ focal length x2 pi, i.s 57.6 degree x field stop diameter/ focal length. Now you get 84.6 degree for the Masuyama 32 (47 mm field stop) which is pretty close to the specification of 85 degree, 81.4 degreee for the Nagler 22 (31. mm field stop) and 100,3 degree for the Ethos 17 mm (29.6 mm field stop). Now, in a strict sense for an eyepiece without any distorsion the AFOV can be calculated by 2x arctan ( field stop / 2x focal length) and now you get 72,5 degree for the Masyama 32, 70,5 degree for the Nagler 22 and 82 degree for the Ethos 17 mm, all numbers significantly smaller than specified (for a narrow angle eyepiece both numbers will be off course equal). Now the question, why did you got 81.3 degree for the Nagler 22 and 77 degree for the Masuyama 32? Both values are larger than expected but in a different way. Different distorsion?

My conclusion, I would not argue that the AFOV of the Masuyama 32 is less than specified, it is common practice to calculate the AFOV just from the field stop diameter. Moreover, at least my impression, the AFOV looks much wider than that of other wide angle eyepieces, e.g. Hyperion 36 mm with is specified with 72 degree.

Thomas[/quote]
I do not do any calculation.
I use the Leica asph 25-50x(75°@50x, which has been measured and confirmed many times) as a benchmark. You can use other confirmed benchmarks such as the Docter 12.5mm=84°.
Then I take a picutre behind the eyepiece and compare it to the Leica via diameter in pixels directly.
Both 81.3° and 77.1° are results comparing with Leica's 50x @75°.
There will be some errors in measurement but I think this is the most direct approach to ascertain an afov.[/quote]

Thanks a lot for your explanations.

A general remark at the beginning, I think it is not so easy to precisely determine the AFOV of wide angle eyepieces. Since I am curios whats going on, I tried to determine the AFOV by using the ' both eyes open method 'explained here,

http://www.cloudynig...is-determined/

see post no. 7

For the Leica zoom at 50x I got 77 degree (according to Leica it should be 82 degree ), for the Masuayma 85 degree. Since it is not so easy to see the field stop from the eye centered position, the error might be a few degree, so the 77 degree for the Leica is a little bit larger than the value you are referreing to, but it seems to me evident, that the field of the Masuyama 32 is quite a bit larger, it seems to be suprisingly close to the specified value of 85 degree. Just by a visual comparison with the Nagler 13 mm it looks to me that the AFOV of the Masyama 32 mm is clearly wider. And this seems to me not so surprising since its ratio between field stop diameter and focal length is larger than the corresponding value of the Nagler 13 mm (17,7/13 =1.35 for the Nagler, 47/32=1.47 for the Masuyama).

On the other hand, you obtained the 77 degree for the Masuyama by taking pictures with a camera and got a field smaller than that of the Nagler 22 mm. In principle I would expect that a photographic method should give better results than the rather cruded 'both eyes open method'. What puzzles me, the field stop in your picture looks very sharp, much sharper than I can see it with my eyes and also much sharper than in your picture 6. Then, if you do a visual comparison, does the AFOV looks narrower than that of the Nagler 22 mm?

Anyhow, for me as important are the field stop diameter and, as already mentioned, the ratio between field stop diameter and focal length. The Masuyama with its huge 47 mm even trumps the Nagler 31mm with 42 mm. The field stop diameter controlls whether Orion's sword or M31 fits into the field of view. For super wide angle eyepieces there is no general valid relationship between AFOV, field stop diameter and focal length, there are different solutions

(see for example here http://www.telescope...t/eyepiece1.htm ),

e.g. a very large AFOV meanig very immersive view and at the same time a lot of distorsion or no distorsion but a slightly smaller AFOV.

With all that said, I would put the Masuyama 32 mm in the class of super wide angle eyepieces like the Nagler line with AFOV above 80 degree, its field of view seems to me at least as wide.Thomas