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I'm well aware of the optical flaws in my cheap bi

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#1 stargazer193857

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Posted 26 March 2014 - 10:47 AM

I'm now well aware of the optical flaws in my cheap binoculars. My resolution is as good as if I were standing half as much closer as the magnification suggests. I can see a bit of chromatic aberration around birds against a white sky background. And when I look down into a beautiful canyon, field curvature detracts from the view. If I look right at a spot on the edge, my eyes can focus and correct the curvature, but I can tell in my peripheral vision that the rest is out of focus. I can see much more in my binoculars and answer my curiosities with them, but the actual image is not as beautiful as with my own eyes. When I follow a star to the edge of the view, even with my eyes correcting for curvature, I still see the star turn into a seagull at the edge in my Nikons, and long before the edge in my $30 binoculars. When focusing on an object, I fine myself wanting to keep turning the wheel to get the focus sharper, and my eyes and brain could take in more information. But it just goes back out of focus. I have to find the spot that is least blurry. Oh, it is sharp and pretty, but just leaves something to be desired.


I'm not in the market to buy better binoculars right now. I just wanted to say I am aware of the flaws of the cheap ones. They are still loads of fun, but I will definitely upgrade after I graduate. Instead of actual binoculars, I want two parallel short telescopes, with no prisms or mirrors, and Nagler eyepieces. The fewer surfaces there are, the less chance there is of mis-collimation and less risk of surface imperfections worsening the view, or other light scatter or chromatic aberration being introduced. I'd much rather have an upside down view if it is sharper. Also, the field stops and index of refraction of prisms limit their apparent field of view. Even for terrestrial viewing, I'd rather be upside down if it means super sharp and wide apparent field of view.


I've also done a little bit of lens system design and research, and I'm well aware of the challenges in getting two surfaces perfectly collimated with each other, including the front and back surface of the same lens. There are just so many degrees of freedom which all must be correct. It is much easier on spherical surfaces than hyperbolic, but still challenging. A little bit off means a bit blurrier. The finer precision you want, the time and effort goes up exponentially. That is why you get diminishing returns with cost.

#2 Rich V.

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Posted 26 March 2014 - 11:37 AM

Glad to hear that your original enthusiasm for and defense of cheap binoculars versus higher quality models has been tempered by experience.

Now maybe we all don't seem like such "optics snobs" as you suspected we were several months ago... ;)

Rich

#3 Stacy

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Posted 26 March 2014 - 12:21 PM

I'm not in the market to buy better binoculars right now. I just wanted to say I am aware of the flaws of the cheap ones. They are still loads of fun, but I will definitely upgrade after I graduate. Instead of actual binoculars, I want two parallel short telescopes, with no prisms or mirrors, and Nagler eyepieces.


You might also consider a bino-viewer. Good ones perform very well and pretty much "get out of the way" letting the quality of your eyepieces and telescope shine.

#4 orion61

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Posted 26 March 2014 - 04:51 PM

Yep I agree. I bought a pair of Arcturus for $120.00 Shipped.
I did have to tweek the Alignment but it makes a big difference on Planetary. Unless you use 50mm telescopes you are going to need prisms of some kind to adjust to your IPD
(Inter Pupillary Distance)

#5 ronharper

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Posted 26 March 2014 - 11:33 PM

SG19,
I too often contemplate such a Keplerian binocular for astronomy. They were actually made in the distant past by Steinheil of Germany--long defunct. Well, Germany is still going.

Your growing acumen is to be envied above any binocular. When you get out of school and start making money, you will no doubt own more expensive conventional prism binoculars, and may find some of them satisfactory. Many of us do.

The Nagler is about as complex as an entire binocular and its edges, although appearing sharp if all that's out there is dim stars, is infected with horrific lateral color. If you're really as optically gone as you say, go with a simpler eyepiece. To be historically correct, a Steinheil triplet!

Ron

#6 RussL

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Posted 27 March 2014 - 04:18 AM

I got by with $30 Tasco binos for years, and had a ball with them, even though I was aware of their deficiencies. Now I own some Nikon Action Extremes, and again I know their limitations, but I still have a ball with them, too. If I could afford better I'd probably buy them. But I can't, not now at least. So, there comes a point at which you just accept what you have and do the best you can. I also live in a red zone. I can't change that either, so I get into seeing what can be seen. As a result I have become a connoisseur of bright objects and richfield stuff. Instead of lamenting I just make use of what IS. When I win the lottery, though,...

Say, you could buy some swell binos for the price of dual Naglers.

#7 Lou3

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Posted 27 March 2014 - 09:01 AM

The good news is that we don't need to drop $2K on European alpha glass (nothing wrong with it if that's what you want). Lots of people are smitten with their BA8 binoculars.

#8 stargazer193857

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Posted 27 March 2014 - 09:35 AM

I definitely enjoy my cheap binoculars. They show me much more than my eyes do. Just saying I'll try to upgrade later.

I wondered how Naglers could correct for color so well without triplets. I guess it may be possible if the distance to retina is well known. You say they have horrible lateral color near the edges? The way people talked about them in the eyepiece forum, I thought they had some of the best edges.

#9 ronharper

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Posted 27 March 2014 - 10:15 AM

Put Jupiter at the edge and you are in for a treat. Yes, it looks sharp enough, but on one side is magenta and on the other chartreuse. A charming color combination, I might have a tie like that.

Ron

#10 stargazer193857

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Posted 28 March 2014 - 02:25 PM

Put Jupiter at the edge and you are in for a treat. Yes, it looks sharp enough, but on one side is magenta and on the other chartreuse. A charming color combination, I might have a tie like that.

Ron


My Huygens do that, but with a narrower field of view, and they do it pretty close to the center.

#11 planetmalc

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Posted 29 March 2014 - 12:40 PM

Instead of actual binoculars, I want two parallel short telescopes, with no prisms or mirrors, and Nagler eyepieces............... Even for terrestrial viewing, I'd rather be upside down if it means super sharp and wide apparent field of view.


As someone who has owned a pair of inverting binoculars (Ross 6 x 42) I can tell you that appreciation of terrestrial beauty is non-existent through them; that girl you're looking at could be Miss World or she could just as easily be the Medusa :shocked: - it's THAT bad!

Astro-viewing is fine once you get used to them.

#12 bakerrihan

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Posted 29 March 2014 - 02:39 PM

me also man
before i bought my bt81s-a i had celestrons 20x80 25x100 barska 12-60x70 and after graduate i will have apm 100 apo
vixen 125bt ,Swarovski ,fiji's 150 and alot of ep's and when i have a place like small farm in our desert (6.5 mag skies) almost 290 days annualy with no clouds .

#13 stargazer193857

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Posted 30 March 2014 - 09:50 PM

Instead of actual binoculars, I want two parallel short telescopes, with no prisms or mirrors, and Nagler eyepieces............... Even for terrestrial viewing, I'd rather be upside down if it means super sharp and wide apparent field of view.


As someone who has owned a pair of inverting binoculars (Ross 6 x 42) I can tell you that appreciation of terrestrial beauty is non-existent through them; that girl you're looking at could be Miss World or she could just as easily be the Medusa :shocked: - it's THAT bad!

Astro-viewing is fine once you get used to them.


Did you compare their sharpness to that of any other 7x binoculars? How good are your eyes? Did you notice a difference? Were colors less hazy during the day time? Did stars look sharper? Do you think prisms detract noticeably from image quality?

#14 ronharper

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Posted 30 March 2014 - 11:28 PM

SG19,
I would like to recommend a book to you: "Telescope Optics" by Ruuten and VanVenrooij, which I have never misspelled, the same way twice.

Prisms, complexity, and the requirement of double telescope alignment limit the optical quality of binoculars, at least badly enough to prevent them from being quite "diffraction limited" like a good telescope. But at their low powers, the telescopes that comprise binoculars can function quite acceptably, if well made.

Otherwise, the hard questions you ask about a Keplerian vs prismatic, I wonder too. That's why I want one.

By the way according to the book referred to, a true Huygens is the ONLY eyepiece completely free from lateral color. So, yours is not quite a true Huygens. That is usual, because in the true Huygens, the field lens is exactly in the focal plane of the eye lens, so every speck of dust is annoyingly evident. So Huygen's honorable design forumula is violated, and lateral color results. Want to know more useless trivia like that? Buy the book!

Ron

#15 planetmalc

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Posted 31 March 2014 - 11:15 AM

Instead of actual binoculars, I want two parallel short telescopes, with no prisms or mirrors, and Nagler eyepieces............... Even for terrestrial viewing, I'd rather be upside down if it means super sharp and wide apparent field of view.


As someone who has owned a pair of inverting binoculars (Ross 6 x 42) I can tell you that appreciation of terrestrial beauty is non-existent through them; that girl you're looking at could be Miss World or she could just as easily be the Medusa :shocked: - it's THAT bad!

Astro-viewing is fine once you get used to them.


Did you compare their sharpness to that of any other 7x binoculars? How good are your eyes? Did you notice a difference? Were colors less hazy during the day time? Did stars look sharper? Do you think prisms detract noticeably from image quality?


The Ross were VERY poor by today's standards (it's an old model - WW1 maybe?) and wouldn't stand comparison with anything I own or anything you'd be likely to make.

You've found a kindred sprit though as I plan to mate a pair of 60mm F5's with my 30mm Widescans for an inverted 10 x 60 with a true field of 8.4 degrees. :cool: These eypieces are not known for their edge-of-field sharpness, even with long-focus OG's, so I'm not expecting it to be fully up to CN standards :shocked:, but it's geeky enough that the moderators might allow me to stay on the forum. :grin:

#16 planetmalc

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Posted 31 March 2014 - 11:20 AM

in the true Huygens, the field lens is exactly in the focal plane of the eye lens, so every speck of dust is annoyingly evident. Ron


Isn't that the Ramsden, rather than Huygenian, problem?

#17 stargazer193857

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Posted 31 March 2014 - 12:26 PM

For full emersion, I would like two tubes. However, mounting them at just the right distance apart, and getting them perfectly parallel, and also paying over twice the price, does make me want to just do the one tube. Even constructing the hole so it is perfectly centered would be a challenge, and mounting the objective collimated with the tube. If it is slightly off, the optical quality would probably end up worse than a stock binocular.

#18 stargazer193857

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Posted 31 March 2014 - 01:03 PM

Well, today I got to do a test with my 16x50 binoculars vs an 80mm f5 and 25mm Huygen and 25mm Sirius Plossl. I do not know if the prism faces perpendicular to the light are coated in either scope, or if the sides are blackened in either. I realize this is an apples to oranges test, but my plan was to compare one prism vs two prisms to see which is sharper.

I aimed at a distant tree, with the refractor mounted and my binoculars hand held. I could not see a difference in detail between my binoculars and the scope, with both at 16x. Maybe a star test will be more telling.

What I did see was that the Huygen had a much smaller view than the Plossl, close to half. The edges of the Huygen looked almost as sharp as its center, which looked as sharp as the Plossl's.

Even though the Plossl has a 50 degree AFOV, and my Nikons a 60*, the Plossl gave me the feeling of having a wider AFOV than the Nikons. I would have to look through both simultaneously to know for sure.

I did not find out if prims detract from image quality or not, but it seems like they don't, and that the biggest limiting factor in my binocular image quality is the shake from being hand held. The mounted refractor gave a better view, although with a little less freedom and a little more set up time.

#19 ronharper

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Posted 01 April 2014 - 08:38 AM

"Isn't that the Ramsden, rather than Huygenian, problem?"


Planetmalc,

You are right, thanks for the correction. Wikepedia (of all places...) has a good summary of the eyepiece types. It looks like what I said about the Huygens would happen only in the special case where the eye and field lens had equal focal length, but I don't think they're actually made like that.

Ron






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