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Will soon examine Orion 100mm RA bino

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#1 GlennLeDrew

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Posted 29 July 2010 - 07:09 PM

A friend will soon take delivery of an Orion 100mm 90 deg. binoscope. Needless to say, as soon as I get the chance I'll subject it to severe scrutiny. Based on other reports here, I expect to find an effective aperture in to 80mm range. I do believe they've already been checked for collimation.

I will determine the position of focus with respect to both the rear prism/window aperture and the top of the focuser, both fully in and out. This should give others some idea of what eyepieces might work, if they first can find out or determine the relevant eyepiece parameters. At any rate, my friend has numerous eyepieces, so for those a direct assessment will be possible.

#2 pcad

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Posted 29 July 2010 - 07:22 PM

80mm range? You probably mean 80mm to 90mm, correct?

As I recall the 88mm version had an effective aperture around 80mm also. Surely the 100mm version will have more effective aperture than the 88mm.

My official guess would be 88mm effective aperture. It would be suitably ironic, if true.

#3 Rich V.

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Posted 29 July 2010 - 08:21 PM

The Garrett version flashlight tested at 80mm:

Garrett 100mm 90° flashlight test

It strikes me as odd that the 100mm model would have the same or less effective aperture than the 88mm? The linked photo sure shows 80mm as does another shot with the flashlight a bit closer.

We'll soon see!


Rich V

#4 GlennLeDrew

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Posted 03 August 2010 - 06:25 PM

I measured the RA-88 as having a working aperture of 77-78mm.

The quite large aperture loss of the 100's must be primarily because its objectives are of shorter f/ratio than those in the 88's. That is, even though the prism assemblies may be identical, the steeper light cone in the 100's will suffer a greater degree of clipping.

It looks like my friend's 100mm bino should be in his hands this coming weekend...

#5 Jawaid I. Abbasi

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Posted 03 August 2010 - 10:15 PM

Glen,
I am awaiting your full report. I have it and it is very good per light throughput. But, I would like to know from a trusted, Well known in the astronomy community and professional and I can see it all the quality gathered in one person. Should I call the name GLENN L. DREW


#6 GlennLeDrew

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Posted 12 August 2010 - 07:17 PM

I now have the bino in my possession, as I have to collimate it (surprise, surprise!). A much more detailed report will follow, possibly in a new thread. Just a few highlights for the moment...

A casual collimation check in the daytime didn't reveal a problem, likely due to the fact that a detail-rich view is easier for the eyes to 'lock on' to and hence bring into fusion quickly. But on the stars the mis-collimation was quite evident, with both vertical and horizontal offset. And the horizontal component is of the bad kind, in that the eyes are forced to diverge outward, in a Marty Feldman-esque fashion.

The total miscollimation, with the 19mm Panoptic (~32X), amounted to an estimated 1.5 deg. apparent, or 2.8 arcminutes absolute (c.f. 1.5 deg. / 32X). This might be fine for your common hand-held 7X bino, but it's ruinous for this kind of binoscope.

Going from memory, this bino shares many traits with the RA-88. The body and rotating prism unit appear identical. The prism apertures are the same, and the pentaprism is as well, probably. Specifically (and provisionally until actual measurements are made), the rear prism aperture is about 22mm, and the 'pentaprism' aperture is nearer to 18mm. The latter, which lies between the pentaprism and rotating Porro-II 'can', is responsible for the greater portion of aperture reduction. The flashlight test revealed a working aperture of 78mm, for both barrels. (The RA-88's working aperture is 77mm, for gosh sakes!!). An aperture reduced to 78% passes only 61% of the light on to the focal surface.

Assuming the stated f/ratio of ~f/6 is correct, then it becomes obvious that for the pentaprism/Porro-II unit used, the objective can be no faster that f/7.7 if the full aperture is to be utilized--and just for the on-axis light cone, at that.

The same 'bar' which is placed near one edge of the rear face of the pentaprism and thus results in a chordal cut-off in the exit pupil is present also, but it may have been placed just a tad farther out of the way than in the RA-88; the clipping of the exit pupil seems to be a bit less intrusive.

The position of focus differs between the left and right. A selection of panoptics and Naglers were tried, and found to be quite close to parfocality. Uniformly, on the right focuser the eyepieces came to focus with the barrel rotated very nearly fully to the top end of travel. The left side stopped rotating a bit before focus was reached. My provisional estimate of the difference is ~2mm. Contrast this to the following...

The objectives are seated at different depths. (The entire objective cell has an external thread, and can be adjusted by spinning it in and out--but it's set with a clear cement.) Recall that the left side's focus was too far out. One might asume, then, that the objective on that side has been seated too far inside. Not so. The left objective is nearly 2mm farther out--I'd like to try spinning it ~2mm farther out yet so as to equalize the position of focus at the back end--IF it doesn't hurt the spherical correction, that is!

The reason I would prefer to make collimation adjustments to the left side is because its image has a bit of a 'flare', to the extent that it's not so easy to assess spherical correction. The right side's image, up to the 67X used for the quick testing through cirrostratus cloud, was nicely round and pretty well spherically corrected--there was only a small intra- and extra-focal difference in the blur circle. The cloud was to thick to allow any kind of reliable indication of color correction (Altair was the star examined).

The objective is a triplet, with a small air space between the front two elements and a rather large space between the middle and inner elements. The spacer separating elements two and three has a somewhat too-small opening, which effectively reduces the clear aperture from 100mm (which I verified by measuring the front element) to ~96-97mm, based on its visible intrusion when my sight line brings the spacer's edge in line with the image produced by the eyepiece. But this is of zero consequence, considering the egregious reduction to 78mm already mentioned.

There is yet another optical element well to the rear, not too far ahead of the pentaprism. As of yet I can't ascertain whether it's a window or a lens having some power.

The insides of the main barrels are rather on the 'shiny' side; they've certainly not been given even the briefest pass of flat black paint. However, so far it seems that in the main this poses no real problem because the extreme baffling (and aperture reduction) 'performed' by the behind-the-pentaprism aperture largely places these untreated surfaces outside direct visible range as seen from the focal surface. (But more extreme reflectance from these surfaces can still make it to the the focal surface by scattering off the walls of the various prisms.)

The focuser utilize compression rings. These rings are narrow-in-width copper (?) bands with the usual slpit, and are actuated by rotating the uppermost portion of the focuser barrel. With eyepieces having smooth barrels, it's all good. But for at least some of those oculars having the so-called 'safety' undercut, they're hell! The spilt ring falls nicely into the 'safety' groove and so in order to be tightened requires turning the upper ring MANY times. And of course, to release the eyepiece the upper ring must be turned as many times in reverse. The somewhat stiff--and FINE--action of rotation doesn't help, either. AArrggh!


Well, how's that for "just a few highlights"?

#7 Jawaid I. Abbasi

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Posted 12 August 2010 - 07:35 PM

Glenn,
So far; you have gone quite in detail. With your initial assessment; do you think it is worth it to keep or look else where in the same aperture?

#8 Joad

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Posted 12 August 2010 - 08:38 PM

The Oberwerk BT 100 just looks better and better.

#9 pcad

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Posted 12 August 2010 - 09:39 PM

The Miyauchi 100mm 45 deg Galaxy looks better and better also. As far as I can tell it has none of the drawbacks listed above.

I'm not shocked but disappointed that all the issues found in the 88 are present in the latest 100 to some degree. Many moaned, including myself, about not being able to use standard eyepieces. Now the proprietary eyepieces that fit and worked well don't seem so bad in retrospect.

Looking forward to your future findings.

#10 charen

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Posted 12 August 2010 - 10:39 PM

Well my Oberwerk BT 100-45* measures 94-95mm. The aperture reduction is via the very front baffle I believe as there is no prism cut off.
94 mm aperture I can handle - but 78 mm !
The Oberwerk does give impressive images - sharp almost to edge with minimal CA. Collimation is spot on even at 80x which is the highest I go to. I believe the front baffle almost helps in reducing CA .
Think I will stay with the Oberwerk !

Chris

#11 Andresin150

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Posted 12 August 2010 - 11:01 PM

Wow Glen, what a pre-servicing report! I guess the Chinese do not master the RA desing yet... hopefully they'll get better with the 150's (as discussed in other current thread)
Appart from collimating them, you plan on doing something about the apperture loss (is it possible to do something, like using, if available, bigger pentaprisms?)
Another question Glen, aside the weight and size, then there is not much difference between the 88's and the 100's, or the 100's, because of their considerable apperture cut, acting like a mask, have longer focal ratio and better CA control?

#12 GamesForOne

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Posted 13 August 2010 - 09:56 AM

The focuser utilize compression rings. ... But for at least some of those oculars having the so-called 'safety' undercut, they're hell! The spilt ring falls nicely into the 'safety' groove and so in order to be tightened requires turning the upper ring MANY times. And of course, to release the eyepiece the upper ring must be turned as many times in reverse. The somewhat stiff--and FINE--action of rotation doesn't help, either. AArrggh!


Frankly I blame the eyepiece manufacturers for this. The barrel undercuts are nothing but a headache and I loathe them.

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Michael Mc

#13 Joad

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Posted 13 August 2010 - 11:07 AM

I swapped out the smooth barrels on my Orion plossls with the undercut barrels on my Orion Explorer zooms so I could use the zooms in my BT100. The undercut barrels are indeed almost impossible in a compression ring.

#14 Tamiji Homma

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Posted 13 August 2010 - 11:25 AM

Frankly I blame the eyepiece manufacturers for this. The barrel undercuts are nothing but a headache and I loathe them.



Hi Michael,

Have you checked out Eyepiece Forum lately? :grin:
The undercut topic comes back once in a while.

Tammy

#15 Mr. Bill

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Posted 13 August 2010 - 12:35 PM

I filled my 24mm Pan undercuts with a strip of electrical tape a couple of years ago and that has worked fine even after many ep extractions and insertions in all temperature conditions. A word of advice....use premium tape, not all electrical tape is equal in terms of adhesives.

:cool:

#16 GlennLeDrew

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Posted 13 August 2010 - 06:32 PM

A minor correction... the compression rings are brass, not copper as I'd initially guessed when peering at them under subdued, incandescent light.

If, as it seems, the entire back end is basically the same as found on the former RA-88, the degree of aperture reduction as caused by the too-small, after-the-pentaprism aperture will be of the same degree.

However, it's quite clear that there is yet more aperture reduction in the BT100 for the following reason. In the RA-88, the focal surface was quite close to the rear prism window's aperture (which required eyepieces having their field stops right down at the very bottom end of the barrel--not commonly found in 1.25" oculars.) But in the BT-100, in order to utilize common 1.25" eyepieces, the focal surface had to be positioned farther away from the rear prism so as to be accessible when the field stop lies farther up inside the eyepiece's barrel. This rearward displacement of focus is the same as 'pushing' the entire prism system closer toward the objective. This then moves an already too-small aperture farther along the light cone where said cone is wider still, which then further reduces effective aperture.

So where we gain in the use of non-proprietary eyepieces, we lose in aperture. Depending on the specific geometry of the entire instrument, the degree of aperture reduction per unit displacement of the prism system along the optical axis will vary. In haven't done a geometrical ray trace of the system, but intuition tells me that if the focus has been moved back by, say, 25mm, the effective aperture might otherwise have been nearer to 85mm instead of the current 78mm.

Indeed, it's my impression that this unit has had its focus moved just a bit too far backward, given that an array of practically parfocal Panoptics and Naglers (all 1.25" format) come to focus at the end of focuser out travel. This could explain the (small) discrepancy in effective aperture reported formerly by some others, wherein 80mm was reported. I wonder if their binos didn't have the focal surface moved as far back as found here?

By the way, focuser total travel was measured at 13.5mm, or just over 1/2".

I did try briefly to rotate the objective cell with a good spanner wrench, but the clear cement is certainly doing its job. If those cells could be turned, the focus might be 'tunable' for the specific assortment of eyepieces one has. A caveat; if the fourth element (which lies not too far ahead of the pentaprism) is indeed a lens and not a window, it may well be that the spacing between it and the triplet objective group is critical.

Another session of peering into the bino is beginning to make me suspect that that fourth element is a negative lens, which suggests a variation on the Petzval configuration. If indeed a negative lens, then the triplet group by itself must have a faster f/ratio than the stated system value of f/6.

I should point out a potential trap for the unwary if they try to assess the correctness of baffle/aperture sizing in any instrument WITHOUT AN EYEPIECE IN PLACE.

In the BT100, with the focuser empty things at first glance look fine. When I sight along the very edge of the objective, I see all baffles/apertures and internal steps ion the main tubes as lining up quite nicely. Were one to not know otherwise, this could well lead one down the garden path, and take it for granted that the full aperture is being used.

WRONG! The reason? There is no way to tell where along the sight line the focal surface lies. This is a most critical 'reference surface', as any sight line must terminate here. With nothing in the focuser, one sees only unfocused light coming from beyond the end of the focuser. There are two ways to see the focal surface:
- Insert a disk of paper 1.25" wide and which has at least a central dot marked, placed at the instrument's focal 'plane'. (One could use tissue paper firmed up with an outer ring of card stock--the tissue-covered hole would then serve as a focusing screen, moved in/out until a very distant scene is brought to sharp focus.)
- Insert an eyepiece which has been set to infinity focus. (Simpler, yes?)

The eyepiece is of course a critical part of the system. Any focal length will do when assessing only the on-axis illumination. From the comfort of indoors, orient the instrument so as to bring into the exact center of the eyepiece image (as seen when looking into the objective) some obvious, compact feature, then lock the bino in place. This centered object serves the role of a central dot on a piece of paper lying at the focal surface.

Now one peers into the objective and moves the sight line off axis until this central feature just reaches the point of becoming obscured by any internal baffle or aperture. If the sight line at this point is not also in line with the very edge of the objective, then aperture reduction is occuring.

The foregoing, which I've brought up here before, is a reminder of what to look for if you're in a shop checking out an instrument. It's great if you'd be too embarrassed to do the flashlight test!


Like the RA-88, the BT100's prism 'tuna cans' rotate on a 'bearing' which is merely a slightly compressed rubber O-ring. Without applying too much force, I can rock the 'tuna' can' through a good two degree range, and while doing so the faint, crackling sound of glue-y grease is heard. I'm confident that all but the most massive of the so-called 'hand grenade' eyepieces should not induce appreciable rocking. I raise the point mainly because the solution used is just plain bad engineering practice. (I have a couple of 45 degree stereo microscopes whose same-purpose bearings are very thin brass 'washers', and the motion is buttery smooth yet as solid as the proverbial rock of Gibraltar.)

#17 Rich V.

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Posted 13 August 2010 - 08:46 PM

Very interesting posts, Glenn.

I suppose most of us have concluded by now that binoculars are an instrument of many compromises. It's a shame though, when any binocular claimed by the mfgr. and vendor to be 100mm falls so far short of spec. I can see (but still wouldn't like) 5% or even 10% less actual effective aperture than claimed but a whopping 22% just goes TOO far. In effect, their "100mm" binocular is the same as their "88mm" model; it's actually a 78mm binocular. They can't just claim that they did this for the sake of removing aberrations by masking the objective!

The idea of arriving 2.8' out of collimation isn't too inspiring either. In this type of "100mm" binocular even 1' collimation error is very noticeable.

Vendors should respect their customers enough to do basic measurements of the products they sell to verify the product is what they claim it to be. There's too much hype in this world already. A bit of QC wouldn't hurt either!

Thanks for the good reading,

Rich V

#18 Jawaid I. Abbasi

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Posted 13 August 2010 - 09:01 PM

Glenn, it make me worried that I paid $1200 but they gave me 77mm. If all true then I am really disappointed though, my Orion BT-100 (BT-77 ?) is giving me nice and bright image but I paid for 100mm and ecpect 100mm full aperture.

#19 Mr. Bill

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Posted 13 August 2010 - 10:00 PM

Glenn, it make me worried that I paid $1200 but they gave me 77mm. If all true then I am really disappointed though, my Orion BT-100 (BT-77 ?) is giving me nice and bright image but I paid for 100mm and ecpect 100mm full aperture.


Welcome to the club....

:p

#20 GamesForOne

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Posted 14 August 2010 - 09:45 AM

I can see (but still wouldn't like) 5% or even 10% less actual effective aperture than claimed but a whopping 22% just goes TOO far.


It reminds me of the monitor fiasco of several years ago where manufacturers labeled the box as a 17" monitor when it only had a 15" display. They counted the bezel too in the 17". :smirk:

That resulted in a class action suit. Generally those only benefit the lawyers, but in that case it did put an end to the misleading specs.

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Michael Mc

#21 Rich V.

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Posted 14 August 2010 - 11:34 AM

Glenn, it make me worried that I paid $1200 but they gave me 77mm. If all true then I am really disappointed though, my Orion BT-100 (BT-77 ?) is giving me nice and bright image but I paid for 100mm and ecpect 100mm full aperture.


Jawaid, I would talk with an Orion supervisor about this. [Moderator edit: it is likely that Orion has no idea what the real effective aperture of these imported binoculars is, so let's not make accusations."]

It's one thing to have a small discrepancy from claimed specs but selling a "100mm" binocular that's really 78mm could be contested as a misrepresentation, IMO.

[Moderator's edit: CN should not be used directly for leverage in consumer-related matters.]

Pictures of the 80mm aperture of the Garrett GBT100-90° were posted back in March of this year. While it wasn't the Orion model, it was assumed that both vendors got their products from the same manufacturer. The chances were good that the Orion would be approx. 80mm effective aperture as well.

The 100mm 45° models haved fared better with measurements from 93mm to 100mm depending on which vendor's version was examined.

I think for now I would be suspect of any 90° model until proven otherwise!

Rich V

#22 Mr. Bill

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Posted 14 August 2010 - 01:10 PM

Glenn, it make me worried that I paid $1200 but they gave me 77mm. If all true then I am really disappointed though, my Orion BT-100 (BT-77 ?) is giving me nice and bright image but I paid for 100mm and ecpect 100mm full aperture.


My two cents....

You're not going to be happy with the 90s so return them to Orion (they are very good about customer service) and buy a pair of The APM 100 45s which Michael Mc likes a lot or the Oberwerk BT100 45s that I own and highly recommend.

It seems that the current Chinese 90 degree binos are not up to par with the available 45s.

:cool:

#23 Goodchild

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Posted 14 August 2010 - 08:21 PM

Glenn,

I really appreciate people like you with your level of expertise because it keeps most people on their toes, not allowing them to say crazy things and get away with it, including vendors/manufacturers (and myself with the following comments and attached disclaimer) that state one measurement and produce something different. However, I will admit that most of what you describe goes right over my head and I sit here asking myself how many more times am I going to have to read a thread before I fully comprehend it? The simple answer is--NEVER. So I end up trying to satisfy myself with the knowledge that I can glean some things from it and be a better/more informed person because of it. And I am. Thank you, and to all of you out there who share their knowledge and expertise with minions like me.

Having said that, let me share my observations re: some of these giant binocs in manufacture today that claim one thing and produce another. I am not an optician nor am I a mechanical engineer, just an observer who wants to get all from their hard earned dollar. However, it seems to me that there are some red flags that should put me and others on alert before purchasing a certain product. The devil is in the details and so I try not to get too bogged down in absolutes and feel more comfortable using generalities--like horseshoes and hand grenades, it's getting close that counts (although I prefer to be as specific as I can when specifics are available). Correct me if I'm wrong if the following assumptions are not true.

I know we're talking about Orion 100mm 90 degree binocs. However, Orion's website doesn't give enough technical specs for me to know for sure so I'll use Garrett Optical specs since they are forthcoming with details and their 100mm 90 degree binocs "look" the same as Orion's, I therefore assume that they are the same. Garrett and Orion advertise these binocs as 100mm f/6.1 which would translate to 610mm in focal length. If 25mm equals 1 inch, then 610/25 would equal 24.4 inches--this should be the overall length of the bino. However, this model is only 15.2 inches long, a loss of over 9 inches in the focal plane. I understand that some of that loss is going to be made up for with the 90 degree turn, but how much? It would seem obvious to me that something is being lost in the translation, but 9 inches? How does one account for this loss? What is it and where is it being cut? Objectives? Prisms? I don't know.

The 45 degree models fare better; however, they are still shorter than they should be (or maybe not depending on how a 45 degree prism affects focal length--I leave that answer to the experts out there). The Garrett 100mm 45 degree should be 21.2 inches long but are in fact 18.2 inches long. The Garrett 150mm 45 degree should be 33 inches long but is in fact 29.5 inches long.

I mention the above because, for me, it's a good rule of thumb when making a purchase of this sort. If the focal ratio and focal plane don't match, it causes me to sit up and take notice that something's not quite right. What I do with that info is another matter. Is this an issue that can be changed or are we going to have to live with it as it is? And if it does get changed, when will it change? Can I wait for that change to occur or do I settle for what's available now? And since I'm considering the Garrett 150mm 45 degree, that question hits home. I hope that by bringing this kind of concern to the attention of observers that the manufacturers/vendors will feel called out and correct this disparity. In the meantime, maybe we'll have to settle for what's available--the market will make that determination.
Royce

#24 Jawaid I. Abbasi

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Posted 14 August 2010 - 10:15 PM

Bill,
I talked to Orion technical department's supervisor before I purchased the binocular and you are right that they do not have any idea about effective aperture.

I am not accusing or believed that it is 77mm but according by Glenn initial findings; it made me woerried.


Royce,
You got some good points but 90mm has torret, inner prism and outer prism so to my best knowledge; it will not easy to figure it out its length.

Well, Glenn is working on it and I am sure he will put up the reports soon (In a manner that You and I will understand)

#25 Jawaid I. Abbasi

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Posted 14 August 2010 - 10:22 PM

You're not going to be happy with the 90s so return them to Orion (they are very good about customer service) and buy a pair of The APM 100 45s which Michael Mc likes a lot or the Oberwerk BT100 45s that I own and highly recommend.


I actually like the 90degree. The 45 degree must be better and effective aperture in between 90-95mm as others report.

If I choose between then 90degree will prefer and it just a personal choice. But as I said above that I rather like to pay for 77mm binocular and keep them. If I pay for 100mm then give me at least 95mm binocular.






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