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And Now For Something Completely Different - Tasco J-B208

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Old Saturday 23rd May 2020, 00:09   #1
dozercsx
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And Now For Something Completely Different - Tasco J-B208

Greetings!
So, I have been expanding my hobby by rebuilding vintage binoculars, and have come across a pearl for backyard/kitchen birding - it's the Tasco J-B208.

What's that you say? Why, it's a high quality, Japanese knockoff (OEM to Tasco) of the Swift Lark 4x30!

(1) it's a Galilean Binocular - it has no prisms of any sort in the path, just two fine, coated Japanese lenses in a beautiful binocular body - ultra-light, yet very quality feeling in the hand;

(2) It's the ultimate extension of the "opera glasses" concept, which max out by design at 4x magnification (just like Galileo's did)

(3) The Tasco's are small - really small - yet quite attractive, and falls perfectly in the hands (rather, fingers). For well preserved copies, expect smooth, quality mechanisms, lots of actual chrome steel bits, and a fine leatherette barrel housing. The optics are coated. They fit just about anywhere - pocket, purse, shirt pocket, leather pouch, you name it (mine came with a handsome black real leather case, with red velour lining).

(4) by comparison to modern prism binoculars, it has a really small FOV - and yet there is something deeply attractive to only seeing what you want to see, rather than a bunch of stuff around what you want to see - pretty much any bird simply fills the field of view - counter-intuitive, and strangely addictive. Also, while not super-sharp images, they do reveal fine detail in birds out to perhaps 60 feet. Plus, they have an interesting, eye-friendly "3D effect" for close objects (close focus is around 10 ft). Oh, and they are Bright - very bright for their size. Their 30mm primaries and low power put my Swift Micron 8x21 Porro and Bushnell 8x21 WA roof to shame in color, brightness and contrast.

(5) The same discussion around 6x30 Leupold Yosemites applies here, even moreso - 4x is supremely easy to hold in the hand (my wife prefers these to anything we have at 7x or 8x for garden viewing) and pending your distance to the subject, can be very effective. Their sweet spot is the distance across a yard garden, or to your suburban back fence. Again, their charms apply for yard bird feeders, kitchen observing, and backyard birding.

(6) I picked these babies up for $10 on eBay. They arrived out of alignment, so I completely disassembled 'em, then put them back together piece-by-piece. Since they are a ruthlessly simple design, it was much easier than expected. Hours of engineering enjoyment later, I ended with something with real charm, quality (I think these look even better than the Larks, with a nicer focus wheel) and something I now use regularly, even with my arsenal of quality binoculars - they are a breath of fresh air apart from our more intense usual discussions on binocular characteristics, and a nice added dimension to any regular binocular portfolio.

Lots of pictures from the rebuild - and if you can find a good example for cheap, give 'em a go - you and your backyard birds may be pleasantly surprised...
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Last edited by dozercsx : Saturday 23rd May 2020 at 08:43.
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Old Saturday 23rd May 2020, 14:28   #2
Binastro
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Firstly, well done on the rebuild.

The 30mm only delineates the FOV in conjuction with the distance front to back.

The actual brightness depends on your pupil size.

The transmission may be high, around 95% if clean.

I presume the objectives are cemented doublets and the eyepieces single or doublets?

I prefer the Dowling and Rowe prismatic 4x22 with 16.5 degree field.

B.
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Old Saturday 23rd May 2020, 14:56   #3
Foss
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Well done Dozer
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Old Saturday 23rd May 2020, 20:33   #4
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Nice job, it cleaned up well. When glass was made to be repaired and not disposed of in a landfill.

Andy W.
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Old Sunday 24th May 2020, 03:15   #5
Patriot222
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They do have charm! Really nice work!
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Old Sunday 24th May 2020, 22:11   #6
dozercsx
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Thanks guys! And, of course, you know what comes next...
All this cool cheap stuff - then you get bit, and buy more binoculars!

Having fallen in love with the simplicity and elegance of this Galilean design,
I went out and bought the new Orion 2x54 Ultra Wide Field Binos!
They are brand new (only came out this year) and are a hybrid Galilean design;
additional lenses have been added to improve the FOV (36 degrees!!), edge focus and
other optimizations. Crazy awesome stuff. And hey, all it takes is money, right? ;-)

Review coming shortly...

Last edited by dozercsx : Monday 25th May 2020 at 00:42.
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Old Monday 25th May 2020, 12:58   #7
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A FOV of 36 degrees can only be approximate and depends how close one can get to the eyepieces.

Similarly, the magnification varies with the user.

Additionally if the aperture is genuinely 54mm, then the outside diameter might be 58mm.
So only those with IPDs greater than 58mm could use it properly, depending also on facial characteristics.

So what is the outside diameter, measured field and measured magnification?
From memory the URSA MAJOR main stars cover 27 degrees. I'll check.

B.
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Old Monday 25th May 2020, 13:27   #8
pat mitchel
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A question about galileans in general: Is there a diopter adjust? Is it a matter of some permanent spacer being installed. Or at such lower power, is the apparent disparity not perceived? Thanks, Pat
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Old Monday 25th May 2020, 13:42   #9
Binastro
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Hi Pat,

I think that the Russian complex Galilean (Dutch) has a dioptre correction.
I'll try to look.

The main problem is that many don't have a focus or IPD correction.

More complex ones have multi element objectives, some with special glass and thick elements.

Wearing glasses drastically reduces fields usually.

Stjerneskinn.com Angular distance between stars is the best one that I just found. I hope it is O.K. for me to mention them.

Ursa Major end stars are 25.7 degrees apart, which I measured previously.
I slightly disagree with alpha to beta.
I have some measures to one part in a thousand.
Measuring maps is useless, and computer programmes not great.

B.

P.S.
Dioptre adjustment is needed to get really sharp views.
The edge performance of some Galileans is terrible and the field often very small.
But the transmission is high generally, and images can be bright.

Beechers Mirage are wide angle using mirrors instead of prisms and available in low powers. They also do Galileans I think.
But very expensive.

Bushnell do the Xtrawide 4x22 or 4x30. Actually 3.5x. Mirror prisms. Fixed focus but great for kids.
Curved field. 18.5 degree field.
Also 5x25 (4.4x about) Nice. Regular prisms.

Visionking 5x25 15 degrees prismatic, but my one is awful in one barrel. Would be great if properly made.

Last edited by Binastro : Monday 25th May 2020 at 14:27.
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Old Monday 25th May 2020, 14:17   #10
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Hi,

the Orion 2x54 state 60-81mm IPD - so not everybody will be able to use them. Otoh with a 27mm exit pupil there is quite a bit wiggle room to look through regardless - the question is how big are the aberrations a few mm off axis?

It seems to have individual focus, so a diopter is not needed - no mention of the focus range though.

Also the massive 27mm exit pupil means that this is always going to be used stopped down quite a bit by your eyes pupil. This certainly helps to keep the aberrations in check (except for those introduced by irregularities of your eye and pupil).

Joachim
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Old Monday 25th May 2020, 14:34   #11
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Hi.

Galileans don't have exit pupils.
The size of the objectives determines the field of view. In conjuction with the length of the instrument.
If one had a small objective I suppose the eye pupil would be vignetted somehow.

Regards,
B.
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Old Monday 25th May 2020, 14:46   #12
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Hi,

I was under the impression they do in fact but not in the classic way of having it where the eyes pupil is (hopefully)... it is inside the instrument and you get a parallel ray bundle of the same diameter as the exit pupil from the eyelens to the eye and thus can get as close a you can stand...

See page 4 lower left image...

https://www.aaopt.org/docs/knowledge...rsn=ce71d384_0

Joachim
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Old Monday 25th May 2020, 14:56   #13
Binastro
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Thanks Joachim for the link.

I thought that this is the case that the exit pupil is inside the instrument.

The large objectives are principally to increase the FOV.

Regards,
B.
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Old Monday 25th May 2020, 15:18   #14
jring
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Quote:
Originally Posted by Binastro View Post
Thanks Joachim for the link.

I thought that this is the case that the exit pupil is inside the instrument.

The large objectives are principally to increase the FOV.

Regards,
B.
Agreed - I guess I should have a closer look at the old galilean opera glass at my parents place when I next get there - although this might still take some time..

Joachim
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Old Yesterday, 08:39   #15
Binastro
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Large true field Galilean (Dutch) binocular.

1). Largest aperture objectives.
Thin strong front walls, maybe machined inner sides.
Observer large IPD.

2). Shortest distance front to back lens elements, but good image quality.

3). Complex objectives using thick glass and ED elements because of short fast instrument.

4). Low power, 1.5x to 2.3x.

5). Good multicoatings.

6). Observer able to get both eyes close to eye lenses. No glasses.

7). Independent focus, hinged.

8) Good quality and reasonable price.

B.
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Old Yesterday, 15:22   #16
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Enjoyed reading this! Very thoughtful comments from all!
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Old Yesterday, 17:11   #17
dozercsx
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Thanks!
A few more interesting observations on the Tasco's (I know the Orions are terribly interesting, but I want the Tasco's (and Larks and their sisters) to have their "moment in the sun" here (bad pun):

While sitting in my yard with the Tasco's:
(1) I measured 8ft close focus with a tape measure, wow! The focuser mechanism gets a bit sluggish in the last few fractions of a turn, but this close range was unexpected, and quite good; and while I have no paperwork, the IPD range appears to be good, very narrow to much wider than my eyes;
(2) The Tasco's are simply terrific for butterflies and other insects - they focus quickly, and are easy to hold (see below)
(3) A strange and wonderful aspect of the Galilean design, which Binastro alluded to above, is that, since the focal point is actually "inside of" the eyepieces, their job is simply to "straighten" the image outward - this has the curious effect of what I call "unlimited eye relief"; what I mean is that, once the bird is in focus in the center of the image, it simply remains in focus, even as I slowly move my eye away from the eyepiece! I tested this up to about 6 inches (!) - what this means is that wearing glasses with these has only a small effect on the view! In ordinary prism binoculars, doing this would have the effect of dramatically shrinking the FOV, but recall from my earlier assessments, the FOV here is quite small to begin with, so the effect is minimized - the bird remains in focus, and the FOV only shrinks a bit. Crazy! The strange experience of holding the binoculars inches in front of your face is unusual - and kind of cool! A new twist on comfort and adjustability.
(3a) another strange aspect of the Tasco's is what I call "focus within focus" - what I mean is that, unlike any binocular I've ever used, within 5-10 feet or so of any given focus point, you can actually refocus on depth of field objects WITH YOUR EYES, and not with the focuser! This is what I initially referred to as "the 3D effect" in my initial text; it's an imperfect description, I know, but it is weird and cool and unusual, and perhaps contributes to the eye-friendly nature of this design... with any regular prism binocular I've ever used, you are simply locked in to the focus point and must turn the knob to refocus on depth of field objects; that's just not the case here, at least in a limited range...
(4) There is no diopter focus, per se, but as per (3) above, wearing any corrective glasses with these should not be a problem - even bottle caps! I did experiment with minor adjustments by turning the barrels ever so slightly, to small effect. The eyepieces rotate, but I don't recommend it as there is little thread friction (hard plastic on steel) and so they flop a bit. Honestly, there is a float in this optical system which makes them flexible. Just tighten things up, put on your glasses, and go!
(5) Finally, there is something about these Tasco's that is just... eye-friendly. I can't put my finger on it, but eyestrain is more or less non-existent.

Oh! Gotta go - my first Monarch butterfly of the season just flew by!

Last edited by dozercsx : Yesterday at 18:00.
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