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71mm Miyauchi Saturn II Binoculars

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Review of 71mm Miyauchi Saturn 11 Binocular

Translation from Italian assisted by fellow CN member Kenny Jones


 In the specific field of binoculars for astronomy , Miyauchi is a name with a reputation for good design and performance.

During spring of 2003 , for the purpose of undertaking a review on behalf of the astronomy magazine for which I carry out instrument testing along with other amateur astronomers , we purchased a Miyauchi Saturn 11 71mm binocular.

This binocular is quite expensive at over 1000 Euros with standard eyepieces and no supplied case , but is quite unusual for a binocular in having a focal ratio of f8 , construction incorporating four elements in two groups with multi – layer treatment.


 Like most Japanese optical products , the design and finish of the instrument is to a very high standard , which at once incites visual pleasure. The 71mm objective lenses showed no defects , bubbles or sctratches. Even the violet hue of the lens coatings matches very well the metalized grey finish of the body.

Other details exude an air of quality , such as the aluminium hull itself , the concentric individual focusing system , Porro prisms tilted to allow 45 degree viewing, constituted from BaK –4 glass ,optimised with mutilayer treatment that supplies luminous and corrected images.

This binocular also came with a 3 x 12 finder with what most people might consider to be "optimal" eye –relief of 15mm. I have read of criticism of this choice of finder , but I feel it is better than no finder at all , especially when using any eyepieces providing magnifications above the "standard " supplied eyepieces ( as are available – see below ) . The standard supplied eyepieces seemed to be of the reversed Kellner variety and provide 22x magnification.



 Upon request I received also two separate sets of eyepieces in order to provide alternative higher magnifications of 40x and 115x.

As a result , I was able to test this instrument on planetary and closer lunar observations . The way these eyepieces fit requires the user to first push in with moderate pressure for approximately two –thirds of the way , then to use a clockwise twist to secure them into their holders.

Adjustment of inter –pupilary distance ( IPD ) is achieved by sliding the PRISMS along two small guides , which is achieved only after disengaging two aluminium locks , which are then locked again once the desired IPD is obtained. The range of IPD is from 54mm to 75mm . These devices for locking and sliding showed no signs of deterioration in terms of fluency or mechanical flaw during my tests.


 Because of the dimensions and weight of the binocular , which is just below 8 pounds , and not having the dedicated mount offered by Miyauchi , we opted for two types of mount to test this with , namely a photographic tripod with pan ‘ tilt head for daytime land panoramas , and a Vixen GP equatorial mount for celestial viewing.

A very sturdy mount is required not just because of it’s weight per se , but owing to weight distribution. The higher it is angled towards the zenith , the more strain the long optical tubes put on the head . Also , particularly at 115x magnification , steadiness of the whole unit becomes even more critical.

When using the Vixen mount we used , special care is needed to avoid scratching the binocular hull with the locking levers , so I concede that it would be preferable to obtain the dedicated Miyauchi fork mount.



 We received the Miyauchi Saturn 11 just in time for the 2003 May 7 transit of Mercury , so decided to use solar filters to enable observation of this phenomena.

IT IS VERY IMPORTANT TO REMEMBER when viewing our SUN through ANY magnifying instrument to ONLY DO SO AFTER covering the OBJECTIVE lenses with very carefully made solar filters. The FINDER SCOPE ALSO needs to be covered or capped to prevent any possibility of accidental eye damage or scorching.

We made our objective covers from solar film cut to overlap the lenses .

Also , to reduce the slight chromatic aberration still present in the form of the thinnest blue ring around the circumference edge , we used two Baadar Planetarium Boosters with slight modifications for the eyepieces. These came in very useful also for viewing the moon and other planets.

 Indeed , I feel it is a shame that Miyuachi does not

 At 115x the sun’s photosphere showed a distinct granular appearance , with various sunspots and a clear separation of the planet mercury against the solar disc.

The "stereoscopic factor" induced by using two eyes instead of one definitely increased one’s perception of viewing a three –dimensional event , when compared with views through telescopes we had set up alongside.

Over the following evenings , we tried the binocular without the solar filters but with and without the modified contrast boosters on the planets Jupiter ( in Leo ) and Saturn ( in Gemini at the times of the observations )

The contrast boosters made a considerable difference.At 40x Jupiter appeared very luminous with surface details not compromised by the effects of the secondary spectrum. Rings of Saturn were clearly visible at 30x but obviously more so at 40x.

During nights of good seeing we used 115x on both planets to satisfying effect.

On Jupiter we were able to perceive some banding on the SEB , the transit of Io and the great Red spot , all comparable to images previously seen through 90mm APO refractors.

 On Saturn , the 115x eyepieces allowed perception of the Cassini division between the outer two rings , distinctly darker tones around the poles and in rare moments of atmospheric calm , even some details to the equatorial region.


 Again using the contrast boosters , this binocular performed outstandingly for lunar observation , for which the range of magnification is particularly useful and interesting.

Please note that some of the following lunar locations and descriptive terms are as expressed in Italian , and my translator friend Kenny has experienced difficulty in finding the appropriate English terminology.

At 115x , Petavius , as is typical during the second day of lunation , was very obvious, with it’s terraced walls and valley rilles clearly discernible , as was Langrenus to it’s north , a pale crater of 127 km. diameter with a small central peak.

 At 40x particularly , image contrast was very similar to that seen through a 100mm APO refractor alongside . Very interesting was the differences in tone between the lunar plateaux and " seas " with secondary spectrum mostly contained , allowing us to enjoy conformations to the lunar edge , including Condorcet C ,Beahim C , Phillips and many others.

Over the following two or three nights , thanks to optimal transparancy of the sky we were able to appreciate almost cinematic effects of the moon moving slowly against the deep dark sky.

During the fourth day of lunation , turning the Saturn 11 towards the zone of Cauchy we were able to admire the "ridge" that extends for 170 Km. whilst unable to identify in any detail , the Cauchy rima . The bowl of Fracastrorius appeared smooth without detail. Within Posidonius , however , we were able to discern the central crater and inner walls.

In the zone of Birt , Rupes Recta was visible , but we were not able to resolve in any detail the Birt rima . Such detail is indeed usually difficult even with a 100mm refractor. Other details notoriously difficult to resolve , but clearly within the resolution capabilities of the Miyuachi proved to include the domes of Hortentius and the widest rima in the Gassendi crater .


 I think it worthwhile and honest to test astronomy instruments not just in optimal viewing locations such as the dark skies of the Italian Alps , but in conditions more "typical" of those the average amateur sky –gazing enthusiast might more easily access . To report on observing sessions from just one or the other could either impress a potential purchaser with excessive expectations or paint a picture less exciting than might be found to be the case in the eyes of a different beholder .

In all cases , with any given quality of instrument or equipment , perception of galaxies and D.S.Os will be directly proportional to sky pollution and atmospheric conditions .

Using the Miyuachis here "as delivered " i.e without the contrast boosters , my overall impressions could be summed up in three comments :

  1. Stars focus to fine points.
  2. Correction to almost the very edge of field of view.
  3. Absence of any apparent distortion.

The images of open clusters such as M44 were VERY satisfying at 22x and 40x -- very similar to those seen through a short –focal length APO telescope , although with a slight personal edge to the Miyauchis owing to the apparent " three dimensional bonus" which only true binocular vision grants the observer.

 For viewing D.S.Os and star fields , an exit – pupil of 0.6mm. can hardly be considered "optimal" , so for such observations , the option of 115x would seem a little optimistic , if not eccentric !

 However , with a spirit of "nothing ventured – nothing gained " rather than genuine expectation , I was pleasantly surprised to find M13 in Hercules at 115x showed partial resolution of stars to the edge of the luminous nucleus , albeit with only moderate brightness.

 The starcluster M3 situated between Arcturus and Cor Caroli was splendid and showed a difference of brightness between the heart centre and the external components . M53 , about 1 degree from Comae Berenicis , and with a magnitude of around 7.5 appeared as a quite weak , not fully focussed sphere .

M81 , M82 and M51 stood out in a deep dark sky in ways commendable for objects usually not noticeably any better resolved in some 200mm telescopes.


 During the tests I carried out with the specimen received , the Saturn 11 model lived up to expectations.

If I were restricted to just two ways to describe this instrument , I would say :


 I use the sometimes misunderstood term "atypical " , because its characteristics seem to place optical performance half way between that of conventional lower magnification binoculars and that more typically associated with telescopes.

There are ( or at least were at the time of writing in 2003 ) very few , if any , alternatives available for a serious amateur binocular astronomer looking for a easily manageable , good quality instrument capable of providing a variety of magnifications.

 It is , I feel , a shame that Miyauchi do not offer eyepieces which would provide an even wider range of optional magnifications to the "standard" 22x ones , between the 40x and 115x currently available at the time of writing.

For example , eyepieces providing 60x and 80x respectively might be more desirable and useful than the ones which they supply for 115x.

Even from first impressions , one feels a certainty of build quality I have come to expect from this Japanese manufacturer.

Optically , celestial images appear to show very high contrast , minimal distortion and with limited , but never annoying chromatic aberration.

The focal ratio of f8 , rare for a binocular , enhances planetary and lunar observation , but is also perhaps more surprisingly , very useful when observing deep sky objects. Considering the relatively long focal ratio , the designers are to be commended for keeping the instrument quite compact.

Throughout all our observing sessions , my friends and I made side by side comparisons with a "trusted " Vixen 20 x 80 binocular , and with the supplied 22x eyepieces , we were all in agreement and quite surprised that the Miyauchi appeared to show greater brightness and resolution.

One would normally expect a handicap of around 10% in objective diameter and 20% in exit –pupils smaller than the dilated eyes , to be insurmountable factors in terms of image brightness , but this proved NOT to be the case.

Quality versus aperture is a long standing and very interesting optical debate.

 My overall impressions of this 71mm binocular is that is it a very good one , with performance on the moon and planets comparable to single lens instruments of considerably greater diameter , and superior in terms of general "user comfort" and "satisfaction" when observing open star clusters and the Milky Way at lower power when compared with the experience at similar magnifications through a telescope of the same objective diameter.

The portability , comfort of "angled " eyepiece viewing , sheer quality of optics and build , and last , but not least , fact that this IS , after all , very little more than a 70mm binocular , combine to make me feel very fond of this instrument , which I highly recommend.

 I have no connection to Miyauchi products , nor have any special reason or incentive to praise any of their products.

 I would welcome any comments about this review , which I hope you have enjoyed reading .

Kind regards from Italy



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