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Vixen SG 2.1x42 Widefield Binoculars

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#1 osbourne one-nil

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Posted 28 May 2014 - 04:59 PM

A bit of an impulse purchase, but I've just ordered a pair of these...should make the summer Milky Way look good!

The spec is...

Magnification 2.1x
Diameter 42mm
Coatings Fully multi-coated
Eye Relief 8.4mm*
Aprox. Real FOV 12.2°*
Aprox. Apparent FOV 25.2°*
Close focus 2 metres
IPD 55 to 74mm
Size 4.6 × 12.8 × 5.4cm
Weight 410g

Has anyone tried these yet? I can see a couple of threads where they're mentioned, but only as a future purchase.

#2 kcolter

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Posted 28 May 2014 - 06:19 PM

I'm fascinated by them, but can't figure out how to get one ordered from the Japanese website listed in another thread on these binoculars. I'm headed to the Grand Canyon in a couple of weeks and would love to give them a try under dark western national park skies. If anybody has any insight about how to order them if you live in the states I'd appreciate the advice. Thanks

#3 ianatcn

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Posted 28 May 2014 - 06:22 PM

I have a pair and am in the process of comparing them with the Kasai Widebino28 which I have had for some time. Trouble is lack of clear skies. They are certainly an impressive instrument with excellent quality in manufacturing and finish. First impressions are that these take the astronomy specific Widebino concept to a whole new level. Look forward to your impression of them.

#4 GlennLeDrew

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Posted 28 May 2014 - 06:31 PM

Ian,
Why wait for stars? A daytime scene, or a cityscape at night are still good subjects for instrument comparison. Chop chop! ;)

This Vixen lists a rather smaller FOV than tbe WideBino. For the same objective diameter, this suggests a longer focus objective, and concomitantly longer (negative) focus eyepiece. Perhaps this spec is conservative; if so getting one's eyes closer will somewhat expand the FOV.

#5 faackanders2

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Posted 28 May 2014 - 06:52 PM

Ian,
Why wait for stars? A daytime scene, or a cityscape at night are still good subjects for instrument comparison. Chop chop! ;)

This Vixen lists a rather smaller FOV than tbe WideBino. For the same objective diameter, this suggests a longer focus objective, and concomitantly longer (negative) focus eyepiece. Perhaps this spec is conservative; if so getting one's eyes closer will somewhat expand the FOV.


They appear similar to the Kasai (previous Blue Planet previous Russian_ 2.3x40mm Galileans.

#6 GlennLeDrew

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Posted 28 May 2014 - 10:06 PM

I looked 'em up online, and certainly see a family resemblance. But the 2.3X40 delivers the claimed 28 degree FOV (64 apparent) when one's eyes are snugged up very closely to the eyepieces. I wonder how much better one can do compared to the (assumed to be conservative) stated FOV of ~12 degrees for this unit? Hopefully rather more so, which the large objectives are after all there to provide.

A reminder: A Galilean's FOV scales as the diameter of the objective. At given power, double the objective diameter and you double the FOV. Provided the eyepiece has sufficient diameter at given separation from the eye. To maximize FOV, get the eye as close as possible; unlike the positive eyepiece, there is no external exit pupil and hence no fixed eye point.

The seeming too-large 'exit pupil' here is a consequence of the large objective chosen to expand the FOV. The light bundle for any one image point occupies only a portion of the objective, this effective diameter equalling the magnification multiplied by the observer's iris diameter. For ever farther off-axis image points, the location on the objective for the relevant light bundle moves ever farther from center to edge. This is in the very same manner that most wide angle camera lenses operate.
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#7 genethethird

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Posted 28 May 2014 - 10:55 PM

I got some last Friday from Mikasa Camera and have been carrying them ever since. The FOV does not increase appreciably between having your eye comfortably placed (the above 8mm seems accurate,) and smushing your eye right up next to the glass. I've never looked through a Widebino to be able to compare. I'd be happy to try any technique you all might suggest to figure out the gain. They focus closer than 2 meters, as I am 5'10" and can focus on my knees. This website has some nice pictures taken through the thing. I was curious about these too, and am very happy with them. Construction is certainly top-notch.

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#8 genethethird

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Posted 28 May 2014 - 10:56 PM

The quasi-useless eyecups from my Baader zooms fit it perfectly...

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#9 genethethird

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Posted 28 May 2014 - 11:18 PM

If anybody has any insight about how to order them if you live in the states . . .


- I ordered off the Rakuten website linked in my post, and I received an email from the Rakuten website proper, and then an email from Mikasa Camera, both in Japanese of course... liberal use of Google translate was not much help. I wired the money to a bank account provided in the second email, and they showed up 4 days later. The communications are all in Japanese- total yen and the bank account info was mostly all I could glean. PM me if you need help with this and I'll forward the emails so you can see what you're dealing with. Not really any trouble at all beyond the language barrier- really good communication throughout, albeit illegible to me (and Google translation, apparently).

#10 edwincjones

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Posted 29 May 2014 - 06:36 AM

If anybody has any insight about how to order them if you live in the states . . .


- I ordered off the Rakuten website linked in my post, and I received an email from the Rakuten website proper, and then an email from Mikasa Camera, both in Japanese of course... liberal use of Google translate was not much help. I wired the money to a bank account provided in the second email, and they showed up 4 days later. The communications are all in Japanese- total yen and the bank account info was mostly all I could glean. PM me if you need help with this and I'll forward the emails so you can see what you're dealing with. Not really any trouble at all beyond the language barrier- really good communication throughout, albeit illegible to me (and Google translation, apparently).



if you do not mind me asking, what was the total cost, including shipping and customs?

I gave up with the bank note and customs cost complication after they would not take a credit card and will wait until available here

edj

#11 GlennLeDrew

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Posted 29 May 2014 - 07:07 AM

These have *monstrously big* eyepieces compared to the ~8mm diameter on the WideBino! This is why for the latter there is a marked difference in FOV coverage depending on eye distance. In this guy the more than generous eyepiece diameter permits comfy eye distance without cutting into the FOV. And the smaller AFoV does help here, too.

With the WideBino, in spite of the small eyepiece diameter, there is much sensitivity to eye centration if aberrations are to be minimized. This is due primarily to the quite strong curvature on its eyepiece surfaces. This Vixen appears to have gentler curves, which suggests greater latitude on eye centration. Can this be verified, or at least be provisionally confirmed?

#12 ianatcn

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Posted 29 May 2014 - 07:20 AM

Ian,
Why wait for stars? A daytime scene, or a cityscape at night are still good subjects for instrument comparison. Chop chop! ;)



This Vixen lists a rather smaller FOV than tbe WideBino. For the same objective diameter, this suggests a longer focus objective, and concomitantly longer (negative) focus eyepiece. Perhaps this spec is conservative; if so getting one's eyes closer will somewhat expand the FOV.


Glenn, I could test by day but given that they are going to be used by me and probably others exclusively on the night sky I feel much more comfortable testing under the stars.

Initial impression of fov was surprising. If eyes are comfortably positioned over the eyepieces then the true field appeared larger in the Vixen. Squeezing the eyes into the Widebino eyecups was required to get a similar field to the Vixen. No exact figures to go on but the Vixen is the more comfortable instrument. The night I first compared them I found that the Vixen was also less critical on eye placement, where the Widebino requires very careful setting of inter-pupillary distance. The conditions I last compared them under had a first quarter moon in the sky but star images at center of field appeared tight in both instruments. Keeping the eyes concentrated on the center of the field and moving the binocular to sweep up objects yields the most pleasing views.

High pressure due in a couple of days so we will finally have some viewing opportunities.

#13 GlennLeDrew

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Posted 29 May 2014 - 08:52 AM

My WideBino (the original Russian version) has had its rearmost perforated cover plates removed, which permits minimal eye distance. And so I can just fit within its FOV the entirety of the Big Dipper, and Scorpius (row of three brighter claws to tip of stinger). This confirms the claimed 28 degree TFoV, albeit via 'extraordinary' measures. ;) With eyepiece perforated plates in place, the max. FOV is about 22 degrees.

#14 ianatcn

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Posted 29 May 2014 - 09:17 AM

Interesting, I was able to get all seven stars of the dipper in the Vixen. In the Widebino the best I could achieve was out to Mizar/Alchor. The early Russian version I have appears to have the periphery of one of the internal lenses frosted maybe to act as a baffle. Did your version have this Glenn? I found it resulted in a lot of scattered light. This is why the Widebino was such a great instrument when I got it - wider field and great stray light control.

When you modified your Russian glass was it easy to remove the eyecups? I am not using mine anymore so may modify them so a friend can make use of them if it is a straight forward procedure.

The coatings on the Vixen are superb. Every bit as good as those on their refractors.

#15 Tamiji Homma

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Posted 29 May 2014 - 09:47 AM

Why wait for stars? A daytime scene, or a cityscape at night are still good subjects for instrument comparison. Chop chop!



Hi Glenn,

Daytime with Vixen SG 2.1x42 wasn't fun as much as night time.

I don't wear glasses so I really can't say for sure but it must have been similar experience as people who have had the first corrected glasses on and seen more immediately.

My impression of using the instrument is that my night vision suddenly improved, going deeper, seeing more stars in empty area, probably mag 1 deeper or so.

Tammy

#16 ianatcn

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Posted 29 May 2014 - 09:59 AM

Why wait for stars? A daytime scene, or a cityscape at night are still good subjects for instrument comparison. Chop chop!



Hi Glenn,

Daytime with Vixen SG 2.1x42 wasn't fun as much as night time.

I don't wear glasses so I really can't say for sure but it must have been similar experience as people who have had the first corrected glasses on and seen more immediately.

My impression of using the instrument is that my night vision suddenly improved, going deeper, seeing more stars in empty area, probably mag 1 deeper or so.

Tammy


Hi Tammy, I found approximately 1.5 magnitude gain over naked eye but on a night the moon was in the sky so compromising my unaided dark adaption.

A brief look under darker skies more recently, I was counting the stars visible within the bowl of Uma and managed 14 through the Vixen, none with the naked eye. It takes exceptional conditions to see any naked eye from here. The price of the Vixen seems little to pay for Super-Vision!

Have you thought of getting one of the night vision head mounts for yours? I thought I would experiment with one but am having trouble sourcing something suitable in the UK at the moment.

#17 GlennLeDrew

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Posted 29 May 2014 - 01:32 PM

Ian,
My Russian unit does indeed have 'frosting' on the eyepjeces.This is a fairly wide, ground conical taper on the edge, which restricts the diameter of the rearmost surface. I presume this was done as a means to aid eye centration. I'd not call it a baffle of any sort, for it does scatter light rather obnoxiously. I painted these conical, ground surfaces black, which very greatly improved things.

The rear, black, perforated caps simply unscrewed. But these also retain the knurled sleeves, which easily fall off now. I placed small strips of masking tape on the inside walls of these sleeves so as to somewhat fill the gaps between them and the eyepiece barrels. This holds the sleeves in place via friction, but with sufficient freedom to turn for focusing.

Interesting that Vixen states a mere 12 degree FOV, while the full Dipper fits within, confirming at least a 25 degree FOV.

Regarding magnitude gain, this is easily calculated. We will initially assume virtually 100% transmission efficiency. And that the bino always operates at the user's pupil diameter, we know sky brightness remains the same, and hence the brightness gain on point sources scales as the square of the magnification.

At 2.1X, the areal increase on the entrance pupil is 2.1^2 = 4.41. The magnitude equivalent is LOG(4.41) * 2.5 = 1.61.

We might subtract at most 0.1m, to account for transmission loss.

Note that for users who are rather farsighted or nearsighted, the eyepieces at infinity focus will be located farther from or nearer to the objectives, respectively. This will result in a respective slight increase or decrease in magnification.

#18 JustaBoy

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Posted 29 May 2014 - 02:03 PM

"Note that for users who are rather farsighted or nearsighted, the eyepieces at infinity focus will be located farther from or nearer to the objectives, respectively. This will result in a respective slight increase or decrease in magnification"


Hi Glenn,

That is something that I began wondering about since around 50yrs ago when I read that there is "a range" of best focus and if we "focused short", that position would give slightly greater magnification.

Thing is, Jupiter (for instance) always looked smaller to me if focused short.

Now then, what I am really wondering about, is if you have to focus to a position that is different than a normal eye on these Vixen's due to being near or far sighted, doesn't the abnormal focus of the uncorrected eye compensate for the greater or lesser magnification you mentioned above?

I mean like, things look bigger to me when looking through Positive eye glasses that are used , and things look smaller with the Negative lenses used by those that are nearsighted.


I have normal focus eyes, except they have long ago forgotten how to do the "short focus" trick, hence the 1.5 diopter reading glasses to type this:-)

Like I said; I am Not Disagreeing, just been wondering for 50yrs:-)

Can you Please :help: Me, Dr. Glenn?

Thanks! :bow:

#19 Mark9473

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Posted 29 May 2014 - 03:46 PM

I was counting the stars visible within the bowl of Uma and managed 14 through the Vixen, none with the naked eye.

This would put your naked eye limiting magnitude as lower than 5.3 and your limiting magnitude through the Vixen at better than 7.3.

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#20 ianatcn

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Posted 29 May 2014 - 04:34 PM

Mark,

Great chart, thank you. Yes, now the moon is out of the sky it will be interesting to do the exercise again. I would think that the differential is probably near to your analysis but I didn't want to exaggerate the difference. I will sketch the stars I can see through the binoculars next time and then come back inside and compare with your chart.

#21 osbourne one-nil

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Posted 29 May 2014 - 06:01 PM

Mine have been dispatched - should be here tomorrow and the forecast is settling down over the weekend, so here's hoping!

#22 GlennLeDrew

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Posted 29 May 2014 - 09:02 PM

Chuck,
If by focusing 'short' you mean that the eyepiece is moved inward (as is done to accommodate for nearsightedness), then we are on the same page.

If I look at a distant scene through weak positive and negative lenses which I can still focus with, the positive lens delivers a slightly increased image scale. And the light grasp is accordingly greater. The same obtains for any afocal optical instrument. By employing lenses to cause imaging-forming light bundles to diverge or converge before reaching the eye, we effectively reduce and increase light grasp, respectively, as compared to the condition of more parallel light entering the eye.

But the effect is not a night and day difference.

Other things being equal (same iris diameter, retinal sensitivity/acuity, eyeball size and eyeglass transmission efficiency), the glasses-wearing presbyope sees a bit fainter (point sources) than the glasses-wearing myope.

But to the individual, whether retaining or removing eyeglasses, the same total correction must be applied in the end, and so there is no real difference in ralative gain in image scale/depth of penetration. Only when the person's eye possesses (and is made to operate over) a sufficient range of accommodation can a difference be discerned.

#23 JustaBoy

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Posted 29 May 2014 - 09:16 PM

"...the same total correction must be applied in the end..."


Thank you, Glenn.

That's what I wondering, exactly!

Thanks again!

#24 genethethird

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Posted 29 May 2014 - 10:50 PM

if you do not mind me asking, what was the total cost, including shipping and customs?



It was exactly 32920 JPY, or around $323 USD. The only fee incurred was the one Wells Fargo charged to wire the money, which was more than I had expected, but as I was already sitting there in the banker's office, I couldn't let that be the deal-breaker.... It came out to total about $370... YOLO


In other news, I took these pictures as carefully as possible from 27.25 inches off the tabletop. The demarcations on the red line are inches, and I tried to get the red line running as close through the middle of the view as possible. First picture, from as close as the ipad lens can get, which is flat against the binocular housing as shown in my pic up above:

*edit* it just occurred to me that the spec given for the close focus is a mistranslation - not 2 meters but rather 2 feet.

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#25 genethethird

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Posted 29 May 2014 - 10:53 PM

-and here's with the camera lens just slightly backed off ~8mm:

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