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Miyauchi - some impressions and questions

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#1 Guest_**DONOTDELETE**_*

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Posted 28 February 2004 - 11:58 AM

I was at a telescope shop earliear this evening to get an extra counterweight for my Takahashi. They had a few Miyauchi models on display (22x60 BS-60iC, 22x71 NBA and 20x100 BJ-100RB), the moon was up, and there were no other customers so I got to try them all. It was more or less as I expected from reading the reviews, but there were a few surprises:

  • The rubber eyecups don't fold down! Very annoying for eyeglass wearers. The shop owner recommended getting another set of rubber eyecups and cutting one down short.
  • The 20x60 seemed to have a wider range of focus adjustment. It was the only one I could focus without glasses. (Sorry, I don't remember how many diopters my eyeglasses are.)
  • The stock eyepieces on the 22x71 have very poor eye relief, much shorter than those of the other two models. And since I needed my glasses to focus, this pair turned out to be completely unusable for me. (Although the cut down rubber eyecups or optional wide-field eyepieces may remedy this situation.)
  • The fluorite models are discontinued. (Not that I could afford it!)

I also tried the Vixen 30x125. I'm very impressed by the view. However the field of view looked even smaller than what the spec says (1.6 degree) - the moon took up almost half the field of view. I don't know if this is a bug or a feature, but I couldn't see the field stop - the edge of the field was fuzzy. Anyway this turned out to be a display model with no manufacturer's warranty, and with a piece missing (the Teflon bearing needed to attach it to an alt-az mount) so I'm no longer tempted to sell my best bike to buy this unit. I am, however, very tempted by the cosmetic blem Miyauchi 20x60 which they are offering for $420. (Yes, I know I just got a Mewlon, but... but... the Mewlon has a very narrow field of view, and I need a good pair of binocs to help with the star-hopping... Yeah that's it... :help: )

Oh yeah, and the question part: the store owner said that the 20x77 has a lot more chromatic aberration than the 20x100 (non-fluorite), despite both being "semi-apo." Anyone know this is true?

#2 holger_merlitz

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Posted 28 February 2004 - 02:32 PM

Hello Ken,

Thanks for your impressions. These are some facts we won't easily find in the brochures.

Looking at the technical specs., the 20x77 model has a length of 32 cm and the 20x100 has got 43 cm. This implies that both should have about the same F-ratio. To achieve a magnification of 20x, the 20x100 then has to use oculars with longer focal length than the 20x77. May it be that these shorter oculars of the 20x77 are more prone to chromatic aberration? Hard to say, here one has to know more details about ocular type and features.

Is this true: Miyauchi is going to discontinue the fluorite models? This could indicate that they are facing some trouble. Do you happen to know anything about the announced new wide angle Miyauchi Binon 7x50W? It was supposed to show up last autumn already, but up to date I haven't seen it anywhere. Hope this one won't be discontinued before being introduced :-)

With regards,
Holger



#3 Guest_**DONOTDELETE**_*

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Posted 28 February 2004 - 07:48 PM

Ken, are there any Kowa sporting optics dealers in your area? Kowa makes an 80mm, fluorite or non, 45 degree ep binocular which is rather impressive. Named the High Lander.

#4 Guest_**DONOTDELETE**_*

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Posted 28 February 2004 - 10:18 PM

About the fluorite models being discontinued, the reason I was told was that one of the lens materials is no longer available. The traditional design pairs the fluorite element with another lens that contains lead. Due to environmental regulations (i.e. the factory that manufactures this glass produces toxic waste) this is no longer available. I think that's why Vixen discontinued the fluorite models, and Borg is redesigning all the ED lenses.

The Binon is not out yet. That's all I know about it.

As for Kowa, I haven't seen one in person. I believe the non-apo 80mm binocs cost $4200, which is why I haven't really looked for one to try.

By the way I found the spec sheet for all Miyauchi models. It lists both the 77 and 100 as having F/5 objectives.

#5 holger_merlitz

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Posted 29 February 2004 - 05:38 AM

Hello Ken,

So the reason is a lens which contains lead and has to be replaced! This makes me think about a general problem in optical engineering:

Imagine we have got a particular optical design, for example the one in Miyauchi's APO. Is it always possible to find a modification so that the use of lead-lenses becomes obsolete, without loss of quality? Are there alternative glass types available, or is it, for example, possible to replace the single lead-lens with a group of lenses which contain no lead? Or, in more practical terms: Is it likely that the modification reduces the aberration control in the Miyauchi, or is it likely that the APOs without lead will be of same quality, but increase in price?

Regards,
Holger

#6 lighttrap

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Posted 29 February 2004 - 07:16 AM

Oh yeah, and the question part: the store owner said that the 20x77 has a lot more chromatic aberration than the 20x100 (non-fluorite), despite both being "semi-apo." Anyone know this is true?


Ken, I can't comment on the 20x77 compared to the 20x100s, but both of the 20x77s I've seen have had LOTS of chromatic aberation. This was of course most noticeable on Jupiter and Saturn, but I was just really surprised how colorful they really were. They were lots worse in that regard than a TV Ranger, (not known for it's freedom from color). I think calling any of these "semi-APO" is really stretching things. To be fair, the Miyauchi 20x77s I've seen were at least a little better than paired ST80s. I'm very curious if the 22x71s don't fix that problem with their longer focal length. However, if you can't use them due to eyerelief, then CA becomes a moot issue.

However, as rboe pointed out in another thread in another forum, it all gets down to how much one is willing to spend to correct color on what may be as few as 6 objects.

Those blemed 20x60s for $420 sound like a good bargain. It'd be interesting to see how those compare to the standard Fujinon FMT-SX 16x70s.

Mike Swaim


#7 Guest_**DONOTDELETE**_*

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Posted 29 February 2004 - 08:57 AM

[quoteThose blemed 20x60s for $420 sound like a good bargain. It'd be interesting to see how those compare to the standard Fujinon FMT-SX 16x70s.

Mike Swaim
[/quote]

My Orion Little Giant II 15x70's (from Japan) at about $250 show better color correction than the Fuji's in side-by-side comparison.

#8 KennyJ

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Posted 29 February 2004 - 12:58 PM

David ( or anyone else )

I suspect my Helios 15 x 70 binos (same as your Orions) have mysteriously been knocked out of collimation ( my 18 year old son and partying friends being one possible source of the damage ) !

Whatever the cause , I was wondering have you any idea how to collimate these binos ?

Although ( or perhaps BECAUSE ) I'm an engineer ( of sorts :- ) ) I am rather reluctant to tamper with anything I'm not really sure about.

Any advice would be greatly appreciated.

Regards , Kenny.

#9 Guest_**DONOTDELETE**_*

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Posted 29 February 2004 - 04:08 PM

Sorry, Kenny, I can offer no guidance, as I've never opened 'em up. If they were mine, however, I imagine tinkering would not be out of the question.

You could always send them to a professional if you goof.

Good luck.

#10 BarrySimon615

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Posted 01 March 2004 - 04:51 PM

Regarding the issue of whether or not the Miyauchi 20x77 has more color than the 20x100 (non-fluorite) Miyauchi, I will comment as follows:

I had always heard (and read some reviews on this as well) that the smaller 77 Miyauchi had less color than the larger pair. This would make sense everything else being equal as smaller aperture achromats can be brought to faster f-ratios without false color becoming a major factor. Knowing this and having read the reviews, I had a certain fear that the larger Miyauchi would exhibit more false color.

Now that I own both the 20x77 Miyauchi and the 20x100 (non-fluorite) Miyauchi I can say that false color is not really a consideration in either. Of course if you look at Jupiter, Venus or the limb of the Moon you will notice false color, but for deep sky observing, it is a non-issue.

I will say that my 20x100's do exhibit tighter stars and the focus mechanism does seem to be a bit tighter (which I like). The focus does shift a bit too easily on the 20x77 Miyauchi.

I love them both - angled eyepieces and eyepiece interchangeability is a great advantage that these binoculars have.

Barry Simon

Attached Thumbnails

  • 63786-Miyauchi 100's on Wagon (left).jpg


#11 Garfield

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Posted 01 March 2004 - 06:34 PM

Barry, thanks for the tip. And as a "newbie" with only three posts, please let me welcome you to Cloudy Nights Binocular Forum. If there is anything you want to ask, fire away!!! ;) :grin: :lol:

#12 KennyJ

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Posted 01 March 2004 - 06:39 PM

I must say Barry ,

These Miyauchi's certainly LOOK the business, quite apart from their performance.

Regards -- Kenny.

#13 Guest_**DONOTDELETE**_*

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Posted 01 March 2004 - 09:15 PM

Thanks Barry for the valuable information!

Do you find that the 77 and 100 are different enough that you use both? Also, is that mount in the photo commmercially available?

By the way I stopped by the shop again and found out that they have the 100 in stock but not the 77. (I forgot to ask the other day.) This might explain why they said the 100 has better color correction. :thinking:

#14 BarrySimon615

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Posted 02 March 2004 - 09:34 AM

I tend to be what is called a "pack rat" in this country. It means I keep things. For me that mostly includes books, chess sets, telescopes and binoculars. Over the years I have had 50+ telescopes (currently about 20) and 40+ pair of binoculars (currently 16, I think). I feel that each has it's purpose, but basically I just hold on to things.

In regard to your question on the 77 and 100 mm Miyauchi, while the magnifications are similar, the weights are different. I can go outside a lot easier with the 6.6 lb (3 kg) 20x77 than I can with the 13 lb. (almost 6 kg) 20x100's. The larger binocular requires a larger mount, while the smaller one works fine on a Manfrotto 3036 tripod with 3063 pan head.

The mount featured with the 20x100 Miyauchi is made by Light Speed Telescopes and is called "The Wagon". It is a Mark II version. Only about 50 or so have been made. It has digital setting circles and gear reduction for very fine movements. Not sure if they are still in production. Here is an e-mail address:

Riddel.LightSpeed@worldnet.att.net

Regards,

Barry Simon


#15 Guest_**DONOTDELETE**_*

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Posted 02 March 2004 - 04:27 PM

I use a pair of Miyauchi 20x77 and I haven't found the chromatic aberration to be a problem even when looking at the Moon. The only shortcoming I see is its relatively small field of view (50 deg. apparent, 2.5 deg. real). But given the physical size of the prisms they use, I don't know if one can go much beyond this.

As far as it being labled "semi-apo", my guess is that the color correction may be slightly better than generic 20x80s, which uses very fast f/ratio cemented doublets. The Miyauchis, on the other hand, use a telephoto lens type optical train. This is usually a positive achromat followed by a negative achromat. So Miyauchis have four optical elements from which a designer can correct various aberrations. Unfortunately, chromatic aberration is not one of them if normal glasses are used. So, you won't see a significant improvement in false color correction.

Also of interest is some differences between 20x77s and 20x100s. Although they both use a telephoto type layout, their prisms are different. The 20x77s and 20x60s use a 45 deg deviating prism followed by a Porro type II prism cluster. The 20x100 uses a 45 deg Schmidt prism followed by a rhomboid prism cluster. In general, Schmidt prisms are harder to make due to its roof surfaces and thus more expensive.

Mike Rhee

#16 Guest_**DONOTDELETE**_*

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Posted 03 March 2004 - 07:33 AM

Thanks Barry and Mike for the information.

I found that the Light Speed Wagon is discontinued. Too bad, it looks like a great mount. I guess I'll have to settle for a Unistar or Unimount if I ever get one of these giant binocs. (Or save up for a Discmount!)

By the way, do the 90-degree and 45-degree versions of the 20x100 use different prism designs? The 90-degree version is a couple hundred dollars extra. (And not as pretty as the 45-degree, IMHO.)

#17 Guest_**DONOTDELETE**_*

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Posted 03 March 2004 - 09:19 AM

The 90 deg version of the 20x100 is probably using a penta prism followed by a Porro type II prism cluster.

Mike Rhee


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