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Equipment Discussions >> Binoculars

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AlbertoJ
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Loc: Madrid (España)
Docter Aspectem 40x80 ED
      #5542908 - 11/27/12 09:50 PM

Hello, Has anyone compared Docter Aspectem 40x80 ED to alpha spotting scopes (Zeiss, Leica, Swarovski, Kowa, Nikon)?
Has anyone compared it to an awesome astronomy refractor like Takahashi or similar?
I´m interested in contrast and image quality.


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BillC
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Re: Docter Aspectem 40x80 ED new [Re: AlbertoJ]
      #5543048 - 11/27/12 11:07 PM

Collect opinions, but realize they are OPINIONS. What you need is a composite of opinions from experienced users . . . who are ALSO familiar with the others you mentioned.

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edwincjones
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Re: Docter Aspectem 40x80 ED new [Re: BillC]
      #5543318 - 11/28/12 06:33 AM

to somewhat answer your question

I got a miyauchi 22x60 pair of binoculars to use instead of a spotting scope, or as a two eyed spotting scope
but
later got a zeiss 65mm 15-45x spotting scope as the scope gave a brighter image at low mag and gave me the option of a higher mag

my conclusion
there is logic to the convential wisdom that spotting scopes work better for long distance birding

edj


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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: edwincjones]
      #5543525 - 11/28/12 10:03 AM

I have the Docters and I'm really impressed with them.

Unfortunately, not too many scopes to compare them with, but I'll comment this:

I also have a Fujinon 40x150ED. I once compared it with an APO 150mm refractor from which I unfortunately forgot its brand. To compare, we used a 24mm Panoptic EP that yielded something like 37x, very near to the Fujis.

Even that the refractor was not a Takahashi, It had terrific optics, totally color free, and the stars where pinpoints to the edge. I have to say that I liked the image more in the Fujis, extension and brightness in DSO's, particularly in bright nebula and contrast in dark/bright nebula where superior considerably, even that the Fujis had slightly more magnification... the joy of using both eyes...

Now, comparing the Fujis with the Docters, the optical differences that I have seen are:

Stars are slightly fatter in the Docters and the image is, of course, dimmer, taking away some extension in some DSO's, or for example, when I observe the Ring Nebula sometimes it even seem like it has color in the Fujis, in the Docters is gray and not as obvious as in the Fujis.
The Docters have an unbeatable AFOV of 84 deg, and the best is that is 100% usable, because of the eyepiece dimensions and its long eye relief, most should be able to take it all, and sharp to the edge, no signs of curvature, coma, astigmatism, etc.. They behave like Apos too.

So, yes, the Fujis see deeper, but the Docters are incredibly near and beat them in portability and AFOV, so I think those should be considered seriously.

I like the specs in the Kowa Fluorites, but I've read that the edges are not as good, even sharper than the Docters in the center but the edges degrade, and their AFOV is good but not as impressive as the Docters. At this point, for me their only advantage is the 45 angled eps (for astro viewing), I really don't even care that is has interchangeable eps, I'm more into observing with one optimal magnification (in binoculars, telescopes need to be more versatile IMO)


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RichD
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5543535 - 11/28/12 10:10 AM

Quote:

The Docters have an unbeatable AFOV of 84 deg, and the best is that is 100% usable, because of the eyepiece dimensions and its long eye relief, most should be able to take it all, and sharp to the edge, no signs of curvature, coma, astigmatism, etc..




An 84 deg AFOV and sharp to the edge sounds to good to be true in a binocular system, are you sure they are strictly sharp to the edge? The term is often thrown around alot on forums like this when in my experience to get an eyepiece in a binocular system with even a sharp 70 deg FOV is a rare thing.


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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: RichD]
      #5543565 - 11/28/12 10:28 AM

Yes Rich, hard to believe no?
Those are incredibly sharp to the edge.
And no curvature, you don't have to refocus to get sharp stars to the edge, it simply shows everything sharply focused trough the entire FOV, and no reflections too. You can place Jupiter in the edge and still clearly see NEB and SEB, thats sharp to the edge to me
And because the quality of its optics, 2mm of exit pupil is not too much, as I thought before I observed trough them.
And you can take all the fov too easily, great ER and not too fat EPS (like in the Fujis)...


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RichD
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5543642 - 11/28/12 11:05 AM

that's very surprising, wider than a Nagler eyepiece and sharp across it. I suppose the higher power helps with this to some degree but it's still very good to hear, must be impressive on open clusters.

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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: RichD]
      #5543943 - 11/28/12 01:56 PM

Yes Rich,
I've been a fan of good optics for a while and I must say that this Docters have impressed me like no other equipment has done in some time.
Nothing in optics should be labeled as perfect, but this Docters are close. I encourage everyone, if possible, to give them a try, the experience using this binoculars is positively unforgettable
They are really not too expensive if you compare them with a couple high end spotting scopes fixed with a couple state of the art EPS.
Concluding, 84 AFOV deg 100% usable and sharp to the edge, Similar to APO performance with no residual color, long ER, not too fat EPs compared with others like the Fujis so will fit most users, extremely portable at less than 5Kg (for their size, magnification and performance),
The drawbacks for some are the fixed straight eps, that for me are of minor importance (straight) and of no importance at all (fixed, which in fact I even consider a plus)


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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5545407 - 11/29/12 11:56 AM

Alberto, if you are buying, be sure that you get the new version.

For example, the version listed in the link below is the old one, look at the eyepieces, those are different, the same wide field but with very short eye relief so it would be difficult to see the whole field and or to use glasses, and also those are not ED and as I've read before, not sharp to the edge and present some residual color...

http://jayscottoutdoors.blogspot.com/2012/11/for-sale-docter-40x-binoculars-a...

I just ordered a new pair from Browe in USA, in Europe you should contact Markus L, he´ll get you the right one. I don't think there are many "new version" ones for sale in the used market, so beware of the used ones unless you can check their version...


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AlbertoJ
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5549344 - 12/01/12 08:11 PM

Thank you very much for reply.

Edwincjones, Docter 40x80 isn´t a normal binocular but a double spotting scope like Kowa Highlander. Then its performance should be like a premium spotting scope.

Andres, I´m interested only in ED version. I knew about Zeiss and Docter old version (non ED), but thank you for advise anyway.

I suppose Docter isn´t as awesome as a quality astronomical refractor like Takahashi, Televue or similar, even at 40x power. I´m talking about pinpoint stars, black background, contrast and CA.
But I´m specially interested in how Docter compares to the last Zeiss, Kowa, Swarovski, Leica and Nikon spotting scopes.
Isn´t there anyone who has compared it to any of them?

Alberto

Edited by AlbertoJ (12/01/12 08:14 PM)


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AlbertoJ
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Re: Docter Aspectem 40x80 ED new [Re: AlbertoJ]
      #5553520 - 12/04/12 08:21 AM

Andres, I´ve seen you´ve got a Swarovski 10x42. Are stars fatter in Docter than Swarovski?
I´ve got a Zeiss FL 7x42 binocular(I suppose similar to your Swarovski in stars) to make me an idea.


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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: AlbertoJ]
      #5553539 - 12/04/12 08:33 AM

Alberto, I'll have an answer for tomorrow, today a new Docter is arriving! tonight I'll compare the stars apparent size with the Swaros. Remember mine are the old 2006 version, just EL, no Swarovision...

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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5555269 - 12/05/12 08:31 AM

Alberto, just clouds last night, will comment as soon as I have some stars visible...

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kcolter
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5555693 - 12/05/12 01:34 PM

Alberto's post made me think again of something I have been wondering about. Is it possible to make a binocular out of a pair of the Zeiss 85mm spotting scopes? I have been very impressed with the image I see through this spotting scope. Perhaps the Docter 40X80 is exactly what I have been thinking about.

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Rich V.
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Re: Docter Aspectem 40x80 ED new [Re: kcolter]
      #5555717 - 12/05/12 01:50 PM

Quote:

Is it possible to make a binocular out of a pair of the Zeiss 85mm spotting scopes?




It's been done here with Swaro 80mm spotters. Something of the sort could be done with Zeiss spotters as well, I suppose. Too bad it can't be done with the 45° versions.

I'm very impressed with the low power astro abilities of the Swaro HD spotting scope. I'm sure the Zeiss would perform well also.

Rich


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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Rich V.]
      #5557197 - 12/06/12 10:11 AM

Still no luck, too much clouds too compare with the Swaros... will try again tonight...
Guess it is the luck with new optics, the new pair arrived on Monday and has not seen a star for the first time

Something important to share, both Docters are exactly the same, I compared them yesterday and it was impossible to tell which one was each.
Before owning them, once Markus Ludes told me that of all the Docters he sold, all of them shared the same quality, and that he couldn't say that of the Kowas in which he saw that some where better than others... That at the time also made me incline towards the Docters and it was very nice to actually see it for myself

Also, I think I forgot when first reviewing them that the only distortion they have is some pincushion, contained but present. I later read that it was introduced to control the rolling ball effect while panning. I don't Know how it works but it is only present when looking at relatively near objects composed with straight vertical and horizontal lines such as buildings. When those objects are farther then it is not noticeable unless you are looking for it.


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Mr. Bill
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5557271 - 12/06/12 10:52 AM

Quote:


Also, I think I forgot when first reviewing them that the only distortion they have is some pincushion, contained but present. I later read that it was introduced to control the rolling ball effect while panning. I don't Know how it works but it is only present when looking at relatively near objects composed with straight vertical and horizontal lines such as buildings. When those objects are farther then it is not noticeable unless you are looking for it.




See this....

http://www.televue.com/engine/TV3b_page.asp?return=Advice&plain=TRUE&...


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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Mr. Bill]
      #5557516 - 12/06/12 01:07 PM

Thank you Bill, very enlightening

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Mr. Bill
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5557685 - 12/06/12 02:57 PM

Kinda comes down to "you can't have your cake and eat it too..."

Like many things in engineering, it's a compromise in design choices.



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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Mr. Bill]
      #5560033 - 12/07/12 09:59 PM

Finally a good night, at least for a couple hours. Alberto, after going from one to another, and because of the image scale things get difficult, I concluded that the stars look slightly fatter in the Docters. The difference with the Fujinon 40x150 is more evident, in it the stars are the finest and sharpest I've ever seen in a binocular
The sky was not perfect but good enough, but allowed me to see some diferences due aperture. For example, the flame nebula in Orion was readily visible in the 150's, in the Docters I suspected it but at this moment I believe it was more my imagination and the fact that I know it is there than actually seen it with them.


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Mr. Bill
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5560725 - 12/08/12 11:27 AM

Well, anyway you slice it, 80mm no matter how good is still 80mm.

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AlbertoJ
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Re: Docter Aspectem 40x80 ED new [Re: Mr. Bill]
      #5563022 - 12/09/12 07:29 PM

Thanks Andres. Now I can imagine how good Docter is.
What´s your preference with it? Astronomy or terrestral.


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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: AlbertoJ]
      #5563062 - 12/09/12 07:59 PM

Alberto, contrary that some would think, I prefer them for Astronomy.

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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5563068 - 12/09/12 08:05 PM Attachment (36 downloads)

Here is something... Just a few minutos ago I confirmed that their TFOV is exactly 2.2 degrees. I used my skysafari iPhone program to confirm it. It frames exactly to the border Aldebaran and star V993. Considering their 40x magnification, should their Afov be 88 degrees instead of 84?

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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5563073 - 12/09/12 08:08 PM

The smaller circle is the 1.7 deg of the 40x150 Fujis...

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JKoelman
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5563885 - 12/10/12 10:15 AM

Quote:

their TFOV is exactly 2.2 degrees. [..]. Considering their 40x magnification, should their Afov be 88 degrees instead of 84?




Amazing specs. Scale the magnification down to reach 3.5° TFOV (still a whopping 25x), and give them a 90° angled view. With the optical quality that you describe, that would be my dream bino.


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Rich V.
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5563955 - 12/10/12 11:05 AM

Quote:

Here is something... Just a few minutos ago I confirmed that their TFOV is exactly 2.2 degrees. I used my skysafari iPhone program to confirm it. It frames exactly to the border Aldebaran and star V993. Considering their 40x magnification, should their Afov be 88 degrees instead of 84?




Could be, Andres. But also consider that they could actually be 38x instead of 40x! The only way you'll know for sure is to verify the 80mm aperture with the flashlight test and then carefully measure the exit pupil with a caliper.

Usually in binos, the stated AFOV includes any pincushion distortion that was added to the eyepiece design. This usually causes a smaller TFOV than stated, not the other way around, though.

Knowing the actual magnification is the only way you'll really know!

Rich


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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Rich V.]
      #5564116 - 12/10/12 12:55 PM

Hi Rich,
I did that a while ago to make sure they where working at full aperture. They measured exactly 80mm, and the exit pupil measured 2mm. Also, the image scale is identical (by appreciation) to my 40x150's...

Also, this brands are known for giving accurate measures, for example the 30.5x are branded that way, not 30x...., and the other measures help confirm it (Objectives focal length 500mm, and oculars focal length 12.5mm)

Math is not working only in the stated AFOV, in some sites (including Docters) the AFOV is stated as 84deg, and in others they say it is 90deg. Math suggests me that it is 88deg

In fact, I measured it yesterday because I thought its TFOV was 2.1deg (I decided then to believe in the 84deg stated), but when I compared the view (with what was shown by my phone astronomy software) I quickly noticed they showed a bit more fov..., then I measured it as exactly as I could...

I've read but not recall where or how, that Afov has another "later/modern" way to be measured and that the results are slightly different... maybe this is the case?


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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5564136 - 12/10/12 01:01 PM

Rich,
I didn't take into account the pincushion distortion, don't know how to measure its influence, but considering that it bends inward, should this cause a larger TFOV than stated instead than a smaller...?


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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5564193 - 12/10/12 01:26 PM

found it..
is was at Nikon's web site
http://www.nikon.com/products/sportoptics/how_to/guide/binoculars/basic/basic...

interesting... maybe they used that formula....


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Rich V.
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5564220 - 12/10/12 01:45 PM

Pincushion increases the magnification with distance from the optical axis. This expands the AFOV without increasing the TFOV.

The newer ISO calculation of AFOV produces a smaller number than the simple method of mag. x TFOV. In the linked example an 8x bino with a 7° FOV would have a 52.1° ISO AFOV rather than the simple calculation of 56°.

Some binos do have a wider TFOV than stated but it's much less common, AFAIK. My 10x35EII binos show stars that are 7.3° apart at the field stop; the stated TFOV is 7°.

Edit: I see you found the Nikon ISO formula I linked while I was typing!

Rich

Edited by Rich V. (12/10/12 01:48 PM)


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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Rich V.]
      #5564263 - 12/10/12 02:14 PM Attachment (19 downloads)

I did Nikons exercise in Autocad..
It worked with their example, but with the Docters it gives just 75deg AFOV...?


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Rich V.
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5564280 - 12/10/12 02:25 PM

Yep. Your Docters at 2.2° and 40x have an ISO AFOV of 75°!

AFOV = 2 x [(inv)tan (40 x tan 1.1°)]
= 2 x [(inv)tan (.768)]
= 2 x [37.526]
= 75.05°



Rich


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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Rich V.]
      #5564291 - 12/10/12 02:36 PM

That brought me back to the beggining... With what math are its specs calculated????

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Rich V.
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5564358 - 12/10/12 03:16 PM

Looking at the specs posted at Euro Optic they state 38.5m @ 1000m which calculates to 2.2°; that's what Andres measured.

That works out to 88° simple or 75° ISO AFOV. Where did this 84° AFOV number come from anyhow? Don't see any reference to AFOV on the Euro Optic site, just TFOV in m/1000m. Any other reference to Docter specs? Can't find much...

Rich


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Tamiji Homma
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Re: Docter Aspectem 40x80 ED new [Re: Rich V.]
      #5564387 - 12/10/12 03:34 PM

Hi Rich,

You can find Docter UWA 12.5 spec here.

Docter UWA Eyepiece PDF document

Tammy


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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Tamiji Homma]
      #5564425 - 12/10/12 04:10 PM

Rich, if you browse in the web, most European vendors state 84 or even 90deg Afov for those binoculars. The individual eyepieces, which are supposed to be the same, even have 84 degrees printed on them....

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Rich V.
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Re: Docter Aspectem 40x80 ED new [Re: Tamiji Homma]
      #5564453 - 12/10/12 04:26 PM

OK, thanks, Tammy! They say 84°.

Oh, well, the simple AFOV calculation is close enough to get the idea. Without knowing the exact angular characteristics of the eyepiece design we don't have enough info to say much else.

It is one really wide field binocular any way we look at it. 2.2° at 40x is remarkable!

Rich


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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Rich V.]
      #5564561 - 12/10/12 05:24 PM Attachment (23 downloads)

After doing some experiments, not too precise but to get the idea, I think that Nikon / ISO are right and according to reality....
I went to a park nearby, and marked 25m away from where I stand 2 points separated 38.4m. Then proyected imaginarily those points half way up (aprox 20m..) and recorded mentaly a circle inscribed in those boundaries. Then, with the Docters I observed, not even focused to avoid distractions, and the projected circle was exactly the same (AFOV). I was even easier to see when only using one eye in the Docters (defocused) and the other eye looking without binoculars, both images (eyepiece borders and the mental projection of the 2 points) coincided.
Autocad has never lied to me... I wonder from where the usual way to measure AFOV came if ISO calculation is simple geometry?....


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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5565640 - 12/11/12 10:02 AM

using ISO, the 40x150's measure 61.37 degrees (29.67m/1000m), with a TFOV of 1.7deg.

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AlbertoJ
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5594075 - 12/29/12 10:20 AM

Hello again.
I´ve seen a parallelogram mount, Universal Astronomics Unimount Light.
Is this mount big enough to charge steady and without shaking a Docter 40X80 ED binocular? or
Does it need an Universal Astronomics Millennium mount?


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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: AlbertoJ]
      #5594099 - 12/29/12 10:29 AM

The Docters weight near 5 kg, look for the máximum load for each mount

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AlbertoJ
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5594136 - 12/29/12 10:48 AM

Universal Astronomics Unimount Light has a maximum load of 12 Ibs, 5.4 Kg.
But I don´t know how steady Unimount is. I´ve read something about this mount. Look at shaking and dampening times at pages 7, 8 and 9 here:

http://www.cloudynights.com/documents/shootout_bino_mounts.pdf

And besides, Docter is a 40X binocular, not a 16X or 20X.


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Rich V.
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5594155 - 12/29/12 10:57 AM

Alberto, I use an older Unimount Light for with my WO 22x70s which weigh ~4.5kg which is the mount's max. rating. The mount works but I would prefer the Millennium mount with it. Damping times are a bit slow at maximum load. Having to use 6.8kg of counterweight doesn't help matters.

The Docters are 5kg and the newer light Unimount is rated for 5.5kg now. You would still be at the mount's maximum. It may work but you'll have to be careful not to induce oscillations in the mount while viewing, particularly at 40x. That high mag. makes a big difference over 15x or 20x.

The Millennium mount would be well worth it if you've made the investment in the Docters, IMO. It would certainly be my choice. Your binos will be well within the bottom half of its weight rating. You will then have the extra capacity to assure sufficient damping at 40x. Make sure you get the Ultra Swing Hinge option which is necessary for comfortable reclined viewing. No point setting yourself up for disappoinment!

Rich


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AlbertoJ
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Re: Docter Aspectem 40x80 ED new [Re: Rich V.]
      #5601864 - 01/02/13 08:05 PM

Thanks Rich, I think Millenium mount with Hinge is the best choice to charge a Docter 40x80 ED binocular on.

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ngc 9999
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Re: Docter Aspectem 40x80 ED new [Re: AlbertoJ]
      #5601901 - 01/02/13 08:32 PM

Have someone tested the field illuination of the 40x80 ED?

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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: ngc 9999]
      #5609762 - 01/07/13 08:47 AM

I'm back
If someone can indicate me how to measure it I'll give it a try....


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ngc 9999
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5609853 - 01/07/13 10:07 AM

Try to line the edge of the objective with the prism edge or baffle and see how much of the exit pupil is blocked.

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Rich V.
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Re: Docter Aspectem 40x80 ED new [Re: ngc 9999]
      #5609946 - 01/07/13 10:58 AM

Andres, here's a great example of lining up the objective edge with the rest of the optical system as provided by Michael (GamesForOne). In the case of the Porro prism Docters, one angle is probably fine:

Photo from the "General comments on angled binos" from March 2010

Rich


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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Rich V.]
      #5611081 - 01/07/13 10:42 PM Attachment (19 downloads)

Ok, I'm trying... Taking pictures of the image circle backwards, depending on the distance, makes the circle change its size apparently (the farther it gets bigger, so I took the pictures aproximately at 15 cm from the glass to get a small one). Pictures are from my iPhone, with not too much light and without flash, not too good but good enough... First, an image of the circle just when it starts to clip... I did a rough calculation and found that it has 100% illumination at 50mm of diameter (49.7mm)...

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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5611084 - 01/07/13 10:44 PM Attachment (19 downloads)

Then, at the edge, the circle has aproximately 50% of its area illuminated....

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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5611087 - 01/07/13 10:45 PM

I'll do this for the 40x150's too, but first I need to know if I'm on the right path...

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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5611094 - 01/07/13 10:50 PM

FWIW, the test was exactly the same at all edges... And contrary to the image you linked, the circle stayed perfectly round in the inner/vissible part... Why in that image the circle seems clipped towards the center too?

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Rich V.
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5611284 - 01/08/13 01:21 AM

Hi, Andres, it looks like your're getting the camera angle right in the second picture. I'm supposing the next aperture seen after the objective edge is the baffle at the first prism face; it's a bit hard to tell.

The linked photo of the 100mm BT shows a small chord cut off by the roof edge of a Schmidt roof prism. Perhaps the prism could have been aligned a bit more precisely to avoid the cutoff. It seems to be common with that particular prism design when used at short focal ratios.

Here's how Glenn LeDrew described this method of assessment of vignette in a thread from several years ago:

Quote:

How to make the sighting when assessing edge-of-field vignetting...

Line up the edge of the objective with the edge of the internal baffle, prism aperture, etc., which intrudes into the eyepiece image the most.

It's that simple. There's nothing ambiguous about it. Even though you are outside the instrument, your sight line necessarily lies on the same path for a ray, traveling from a distant object, which passes through the objective's edge, is refracted and then just clears the most intrusive aperture before reaching the focal surface.

If this ray/sight line is at the same-side edge of the eyepiece image circle (as the Miya Saturn III nearly achieves), the circle of full illumination is as large as the field stop. Yippee!

If this ray/sight line is halfway between the same-side edge and the center of the eyepiece image circle, the circle of full illumination is half as large as the field stop. Nice!

If this ray/sight line appears to intersect the center of the circle of the eyepiece image, the system is fully illuminated on-axis [only]. That's OK!

If this ray/sight line appears to intersect the circle of the eyepiece image beyond the center, the system is not working at full aperture. Boo!

When taking a photo, try to observe these conditions:
- Set focus to infinity, as the eyepiece's image (and field stop) will be collimated by the objective and hence optically lie at infinity.
- Move the camera farther back so as to obtian better focus on the objective's edge.
- Illuminate the objective edge so that it can be readily seen. The camera's flash can help if it's not blocked by the bino's lens shade, etc.




Rich


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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Rich V.]
      #5612488 - 01/08/13 06:42 PM Attachment (15 downloads)

Well, i tried some images with the flash on. It is evident that there is no cutoff, the prisms seem bigger than the eyepiece field stop.

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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5612492 - 01/08/13 06:44 PM Attachment (15 downloads)

If I go farther away to take the photo, the circle begins to grow... I was like 1.5m away....

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Andresin150
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5612500 - 01/08/13 06:47 PM

In the 150's I've observed almost the same behavior, but the circle needs more distance to grow compared with the 80's, maybe because of the difference in the eyepieces Afov?...

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Rich V.
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Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5612525 - 01/08/13 06:58 PM

It's the off axis illumination shot down the optical path from the objective edge like in your second original photo that shows vignette. I wouldn't expect any on-axis problems and don't see any!

I would love to see similar off-axis shots taken through the Fuji 150s. We're looking for the "cats eye" shaped aperture at the eyepiece end of the optical train while sighting along the objective edge. That's what shows the degree of off-axis illumination of the binocular. This is what Glenn's instructions are about.

The off-axis illumination differences between the 25x150 and 40x150 would be most interesting! I'd expect a bit more vignette at 25x than 40x...

Thanks, Andres!

Rich

Edited by Rich V. (01/08/13 07:11 PM)


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