My own experience on 25x150mm UO Binos
Posted 03 July 2009 - 05:45 AM
First of all, forgive my english, as I am french, I will surely make some big mistakes, but I hope that I will still be undestandable.
So, I received 3 or 4 weeks ago my UO binoculars 25x150mm (with 2" interchangeable eyepiece) with forkmount, tripod, 2 eyepieces 25x, 2 eyepieces adapters 1,25". Binos are in very nice white color and were very well protected in pvc and iron case.
First impression, was very good quality for binos (design and mechanical quality). I quickly set up binos on fork and on mount, and found that stability was very poor. A small quick on binos make the fork shake a lot. I was wondering if I correctly install the different parts of the mount, especially for one small piece and contact reseller to be sure. At least, I invert this small piece and after correcting this the stability was fine enough.
As it is Alt/Az mount there are two lock system (two screws for Alt and one for Az). The Alt lock is good, but found that Az lock was not strong enough, you can still easily move the binos even after strongly screw the Az lock. When you unlock Alt/As moves are really, smooth.
First look outside : My first night outside was, in my garden with lot light pollution. For this first try I use the two eyepieces provided with the binos, and plan maybe to buy one more set to reseller (after all interchangeable eyepieces is one of the most important quality of this binos). It was my first light in big binos, I previously look in differents scopes with differents apertures (8" to 16"), so first impression was the impressive FOV... and the big, big, big.... comfort to look with two eyes. It is like rediscover the sky, be in the sky, some kind of sky trip. What I mean, when you observe in scope with one eye, you know that you have two feet on earth, with the binos it is like travelling in the sky... But I guess it is the same for all binos. So what about optic quality... Firt look was low light stars, with nice color and pinpoint, then I jump to lighter stars to detect chromatism problem, and then I was not really satisfy, I saw blue and red color on each side of the star, and maybe more on right tube that on left tube. I turn the binos to moon and also see blue and yellow color around half the moon... I first wondered if it was some collimation problem, and move forward and backward focus, but airy was quite good, very symetric and very similar on backward and forward. I have also tried to modify collimation of binos, but you can only change the prism collimation and image parallelism, if one lense has moved you just can send back the binos to reseller. Before do that I tried other eyepieces, and at least the image was really much better, few chromatism, depending also a lot on your eyes position. One advise is to be really careful at your eye position to get the best image quality, you have to carefully center each of your eye. This operation is not really easy because the two part of the binos that contain the prism can be moved manually to change eyepiece distance, but because this two parts are heavy when you do not keep your hands on them they slowly move down... Keeping your hands on them, mean that you will have vibrations on the whole binos. Which is, you can believe me, not optimal at all. So I have to disassemble the small part that join the two prism olders (I am sorry if I am not clear, but I do not know how you call this part in english, if some people needs help I will try to be clearer in future posts)and put a rubber joint, and so it does correc the problem.
One more issue, it is that not all eyepieces are working on this binos as it is stated by reseller. I bought two Baader Hyperion Zoom eyepieces and was not able to focus, it was also the same with other eyepieces. Reseller told me that normaly all parfocal eyepices should work... I did not know that Baader Hyperion was not parfocal...
So At least my impression is, this binos are very good mechanicaly and optically but you will have to make some improvement or ask your reseller to do it for you. And, to do not waste binos quality carefully choose the eyepieces you will use, because it seems that this binos are more sensitive to eyepiece quality than scope I previously owned.
Hope this help, I will be pleased to answer your questions.
Posted 03 July 2009 - 06:18 AM
I also get the color on the brightest stars and planets with my 25x150 fujis and 100mm miyauchis florites
Posted 03 July 2009 - 06:41 AM
Posted 03 July 2009 - 06:44 AM
A warm welcome to the binocular forum.
Posted 03 July 2009 - 06:55 AM
Posted 03 July 2009 - 07:45 PM
If you look backward, through the objectives, do you see the round field stop, or is part of the field stop obstructed by a prism housing, or some other protrusion which should not be there? That has been a problem with some of the Chinese inclined view binoculars( and with some of the straight view ones also).
Posted 03 July 2009 - 08:31 PM
Since these new Chinese 150mm have been made to use eyepieces designed for use with telescopes without prisms, one supposes that the optical designers balanced the aberrations of the objectives and prisms, and let it go at that. That would clearly be suboptimal, but by how much, and for which of the several aberrations, and for what field sizes, etc? Clearly, this is a complex topic. One might consult the design suggestions by Robert Hopkins, in Mil Handbook 141, available on this forum , for an example of aberration balancing in a prismatic telescope. That was before ZEMAX or OSLO, but the basic principles have not changed.
Is there/will there be, an eyepiece, for 26 x or that region, optimized for use in those binoculars(rather than just something already existing for mirror telescopes)? Or would such optimization be of little consequence at f/5.5?
In the recent thread by EdZ, about ED glass, it is pointed out that a much larger part of chromatic axial aberration is due to the objective, than to the eyepiece, reading information via Roland Christen, it says. But there are other axial aberrations, and field aberrations.
Are they reverse engineering the 1980's right angle version of the Fuji 25 x 150 I , which looks very similar? If so , I hope that they are using a larger pentaprism. Or, are they adapting a Miyauchi ?
Posted 04 July 2009 - 02:59 AM
Posted 04 July 2009 - 02:40 PM
But my question was about looking through the large front lenses, in reverse direction.
Posted 05 July 2009 - 02:19 PM
Posted 06 July 2009 - 01:45 PM
Posted 06 July 2009 - 02:14 PM
Posted 06 July 2009 - 03:41 PM
When I look front of the binos, I can not see something, like a prism, that stop the field.
When looking into the front end of a binocular you
would be able to see how the prisms cause vignette in the system;
would be able to see if a baffle is stopping down the system;
would not ever be able to tell if a prism aperture is stopping down the system,
even if it is.
Posted 07 July 2009 - 08:49 PM
Thank you very much for your report on these binoculars.
You say that there is something in the light path when you look through the front end, the big lenses? This is also a problem with with the 4-inch binoculars. For $4000 (U.S.) this should not be. And why is there a glass window in front of the prisms? Are these water-proof or filled with nitorgen? I am not certain, but this glass may harm the image sharpness and also cause a little chromaticism.
Please post any more thoughts you have on these.
Mkie Rapchak Jr.
Posted 08 July 2009 - 03:14 AM
Posted 08 July 2009 - 04:08 PM
Re: Aberrations from the sealing window. These would be of the same type as those from the prisms(which are very thick glass block windows, from a aberration contribution standpoint), and would be negligible for a window of that probable thickness. Aberrations of prisms are discussed by Hopkins in Mil Handbook 141, available in this thread.
For example, the cone on those is about f/5.5, we read. Consider the WW II Busch design 10 x 80, 45 deg inclined flak binocular, at f/3.5. A 3.5 cone is much steeper than 5.5. The problem is non-linear, as I recall, so the situation is probably worse than just the ratio 5.5/3.5. That version 10 x 80 has selectable internal gray (early production colored) filters and a clear window "filter"( to avoid refocusing when changing from filtered to unfiltered view, such as when the searchlight beam left the field of view, and she wanted to find the fire-terror bomber Lancaster on a moonless night).
Except for a minor refocus, I see no difference in the images of 10 x 80 specimens in which the internal window clear "filter" is intact, and those on which I have removed the window. The windows are uncoated, so there is some light loss from each surface. Incidentally , those can be made hand-holdable by removing the filters and the mostly steel filter mechanism, the steel dovetails,the steel reticle illuminator collar etc. I have replaced the eyecaps with Delrin, the IPD dovetail with Delrin or aluminum shorter versions, the IPD gear with brass setscrews, and the IPD L-slides with Delrin or aluminum (some were originally aluminum).
Posted 08 July 2009 - 04:26 PM
Posted 24 July 2009 - 07:56 AM
Again IPD is fine for me, but I think minimum UPD is really too big, I have problem to put my nose between eyepiece, I found more confortable and better view by looking 1" behind eyepiece even if you lost some FOV.
Posted 24 July 2009 - 08:49 AM
Posted 24 July 2009 - 02:05 PM
I'm watching with interest....the 90 degree model.
Posted 27 July 2009 - 04:07 AM
It's going to take time to get first hand reports on these in the USA....APM America would be the logical choice and first examples are being delivered now or soon.
I'm watching with interest....the 90 degree model.
It is said that the 90 degree model has once more reflections than the 45 degree model does.
Posted 27 July 2009 - 07:13 AM
Posted 30 July 2009 - 11:26 AM
Posted 30 July 2009 - 04:27 PM
The usual way to make a roofless 90 degree inclination is with a pentaprism, followed by a Porro prism cluster with 4 reflections. The two reflecting faces of the pentaprism need to be metallized or treated with multilayer dielectric coatings, because the light incidence angle is too low for total internal reflection.
If a roofed Amici prism is used for the 90 deg. bend, the roof splits the converging light cone. That causes interference/polarization effects which degrade the image. The roof angle must be very close to 90 degrees, or double images occur. The use of mirrors to make a huge virtual prism, or phantom roof "prism", or mode II Amici prism , from air instead of glass, avoids those two problems. In those, the light cone is not split. There is no material roof line. We discussed those in a February thread, illustrated by Mil Handbook 141. Inclination can be 70 degrees, approximately, up to 180 degrees.
For roofless 45 deg inclination, two mirrors, or their prism equivalent, are followed by a 4-reflection Porro cluster.