Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
Get a Cloudy Nights T-Shirt Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu uh, User

Equipment Discussions >> Binoculars

Pages: 1 | 2 | 3 | (show all)
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
Best binocular overall or in a given price range new [Re: EdZ]
      #153415 - 07/22/04 11:36 AM

There's a lot of opinion about what's best, but this thread highlights links to some very good choices and makes a few good points for the buyer to watch out for.

In this link you will find a well organized presentation of suggested binoculars put together by Mike Swaim. While originally prepared for the purpose of recommending to beginners various binoculars for specified use or price ranges, Mike's gathering and organization of information leads us to a collection of short reviews within product lines. Mike touches on over 30 different binoculars in this very worth-while post that groups binoculas by powers and by price ranges. Along the way, he explains a few simple things the beginner needs to know when shopping for a good first binocular.
Light Trap's beginning binocular suggestions


Best all purpose binoculars for under $100


And this thread dedcribes one user's approach to "inexpensive" <$100 binos.
Got my Skymaster's



Several recommendations here lead the buyer in the direction of how to get the most for a $400 budget. Is that $400 just to buy the binoculars or to buy the binoculars and a good sturdy mount? How much binoc and mount can you get together for $400???

$400 Budget What do you recomend?


On a similar note this forum participant has outlined his process for making a decision on which criteria mattered most in his decision for an under $500 100mm binocular
The 100mm bino market in the $500 price point


This poster started out by stating "My budget is about $700 for bino's & mount". You'll soon find that forum participants here love to spend other peoples money. In the thread "So many topics & STILL no definite answers" we give our suggestions ranging from $425 for a used Fujinon 16x70 to a discussion about the $1500+ Oberwerk BT100.

$700 for bino's & mount.


Now, if you like premium optics in small packages here is a comparison of two premium Nikon 42mm optics

$800 to $900 buys Nikon premium 42mm binocs


Several Top of the line 12x50s Nikon, Leica, Zeiss
Strengths of Nikon / Leica 12x50s to a potential premium 12x56


Here's a good question. It asks whether or not it's better to spend more on a higher priced 16x70 or a lower priced 20x80 that might just be able to "beat out" the 16x70 in certain observations. And if that's true, why spend more?

Which of these tripod-use binoculars would you judge most likely to deliver the best performance in center field resolution, contrast and limiting magnitude: Fujinon 16x80 or a generic 20x80 like a Burgess LW, Anttlers or Barska?
16x70 Fujinon or 20x80 generic?
Contrast is the one characteristic of the view that you can't tell by the numbers. It is almost always increased in quality instruments and is lesser in bargain instruments.


And finally this thread has a very good discussion on high priced but superior quality binoculars. This is not best bargain in a particular price range. This is a discussion of what our members feel is the BEST out there.
What is the Best Binocular for Astronomy?



Edited by EdZ (02/13/10 09:35 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
Favorite Binoculars in Various Sizes new [Re: EdZ]
      #153416 - 07/22/04 11:37 AM

The following post includes some excellent binocular choices and some all around good advice. It is worth the read.
"This list is NOT a "best of" list. Nor is it all comprehensive. It's not even a list of all the binoculars I've owned, much less tried. This list IS an attempt to give people some idea of where they might want to begin their shopping." - Mike Swaim
Mike's Recommendations - And Sound Advice


"Let's say I got wiped out by fire or theft and got an insurance check to replace the 15 pair of binoculars that I now own, what would I do? Here is what I would get (from top to bottom)." - Barry Simon
Barry Simon's List of Favorites


"while I have 150 models in my cabinets, that doesnt begin to scratch the surface of whats available. I do have a right to discuss what I own or use." - Bill Cook
A few of Bill Cook's favorites


"Just another opinion: I'd may well get the binos I have now." - Stephen Tonkin
Stephen's Short List


Various members here respond with a list of their favorites in Bill Cook's Favorites
Holger Merlitz, EdZ, Bill Cook, Kenny J.


Edited by EdZ (02/13/10 09:34 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
Affect of Eye Pupil on Binocular Aperture new [Re: EdZ]
      #153417 - 07/22/04 11:38 AM

Affect of Eye Pupil on Binocular Aperture THREAD

A complete explanation of why you should take into consideration the maximum dilation of your own eye pupils before you consider what size binocular to purchase. This explains the implications of using a binocular with exit pupils that are larger than your eye pupils.

In a nut shell, if you are using a binocular with a 7mm exit pupil, for example a 10x70, but your eyes dilate to only a maximum of 5mm, then your binocular is effectively performing as if it were 10x50. You gain no more light gathering, brightness or resolution than the maximum exit pupil allows. In this case the maximum exit pupil is controlled by your eyes and would be limited to 5mm.

A collection of my various posts on this topic and predominantly modified and corrected to the information in the thread above led to publishing this article

Affect of Eye Pupil on Binocular Aperture CN REPORT

This information is just as relavant to a telescope user who is attempting to maximize brightness of image by using the largest possible exit pupil that the equipment on hand will allow. In the same manner as stated above, if the exit pupil exceeds the maximum dilated eye pupil, then you are reducing the effective aperture of the scope.


A member asked "I think these are great binoculars...BUT... I find they amplify sky glow or produce it? ... Is this because of the rather large exit pupil(7.1mm)? I don't see this glow in my 15x70's and I'm guessing that it's because of the 4.4mm exit pupil or the higher magnification." Binocular newbie confusion about Exit Pupil
This reply addresses both too large exit pupil, which can generate washed out images, and also too large eye pupil which can decrease effective aperture.



edz

Edited by EdZ (02/13/10 09:33 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
Philosophy and Binocular Ownership by Bill Cook new [Re: EdZ]
      #194850 - 09/12/04 03:30 PM

And even more thoughts of philosophy, quality and ownership
Bill Cook on Binocular Ownership - 2012

More thoughts and philosophy on quality and binocular ownership
Bill Cook on Quality - Feb 2010

Optics Philosophy, Product Info and the very personal aspects of Binocular Ownership

We are reminded of some important things we should remember regarding the industry and the rags that tell us about the optics and how they perform. Thanks Bill.


this post by infrequent participant, but always well versed, Fiske, lays out
10 Reasons to Spend $1000 on "Little" Binos.
Certainly not for everyone, but it is a philosophy on ownership, for some, that is stated very well.



edz


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
What can be Seen in Various Sizes Binoculars new [Re: EdZ]
      #200431 - 09/19/04 06:21 PM

This post collects a summary of the views of a selection of items through various sizes of binoculars from 10x50 all the way up to 22x100s, 25x100s and a BT100 binocular telescope with changable eyepieces from 24x100 to 62x100. It is not intended as a post on the differences in quality between binoculars. It's intended to give an indication of the differences in the VIEWS between various sizes.
Next BIG Binocular, How BIG!


More Comparisons
Observations and Comparisons with 8 Binoculars from 8x56 to 44x100

Here's the record of a handheld observing session with nikon SE 10x42s
Binocular Serendipity

Here's a report from a viewing session with Oberwerk 25x100s
A cool August night with Oberwerk 25x100s

Views of globular cluster M26 Scutum and Planetary neb M57 Lyra
Several small binocular handheld observations and several mid-larger binoculars on the same objects


Deep Sky Observing with 70 , 80 and 100mm Binocs
Galaxy Hunting with Oberwerk 25x100


What can be seen with 16x70s?--a report
Some of these objects are a struggle for a 20x80 or a 25x100. But in this observing session under dark skies you can read what can be seen in ~mag 6 skies.


The lowly 15x70 Skymaster under really dark skies
A very nice observing report using a binocular we often refer to as lower on the scale. But you will see from this report, they are very capable.


How many stars should I be able to make out in the Trapezium through 11x56 binoculars?
For the answer to this question, see the discussion here
The Trapezium in Binoculars


and this exceptional observing report using 8x42 binocular
Finally a few steps up the Bortle scale.
the advantage of a very dark site cannot be overstated


What Binoculars for Viewing Planets?
Here are some good summaries of various sizes of binoculars and magnification that will allow you to observe some of the phenomenon that we look to the planets for. Disks, rings, moons, phases, shadow transits.


Surface Brightness (Sb)
Observing faint extended objects such as galaxies is complicated by the fact that books generally list the visual magnitude, but a better indicator of whether or not the object might be seen is Surface Brightness (Sb). Read this brief explanation.

Visual magnitude of an extended object would be the magnitude if you could compress all the light of the object to a size of 1 arcminute area. Surface Brightness of an object gives an indication of how spread out the light is and how faint it will really appear.

For an object like M101 that has a visual magnitude of mag 7.7, but an area of diameter 26 arcminutes, that light is spread out over 530 square arcminutes. Hence is has a very low Sb = 14.7. That is averaged. As you get out towards the extremities, it is fainter, in towards the center it is generally brighter. So for instance a galaxy with a bright core might be visible, but it would appear much smaller than its full size because you can see the core but not the extension.

M101 has some brightening towards the core, so the core area actually has a little brighter Sb than 14.7, while the extremities have a fainter Sb than 14.7. Another example is M33 in Tri at Sb 14.0 was easy, this one also has a broad brighter core, so in these cases we generally see just the brighter core area.

Take the example of a DSO listed as visual mag 7. If the object is 10'x10' then it has an area of 100 sq arcmin. The light would be spread over an area 100x greater than the compressed area used to determine the visual magnitude measurement. It would actually appear 100x fainter than the visual magnitude. A light difference of 100x is 5 magnitudes so the Surface brightness of this object would be Sb = 7+5 = Sb mag 12.0.

edz



These records above of what can be seen in various sizes is all well and good, but let's not lose sight of the simplicity of binocular viewing. Here's a post from a thread titled What's Your Use for binoculars?

Few people claim to be able to hand hold 15x70s. Although I rate a pair of Oberwerk 15x70s or my Fujinon 16x70s near the equal of a low power telescope, I am not among those that can hand hold such a size and I use these sizes mounted. So I will relate to you how I grew to enjoy binocular astronomy with my handheld Orion 10x50s.

Many a night I would gaze upon clusters such as the Pleaides and the Hyades. I learned intimately the positions of the stars that make up these wide asterisms. I would spend evenings lying about searching out all the globulars I could find. In a night M3, M92, M13, M5, M10, M12. On another night M4, M22, and all the populated open clusters of Sagitarius. The M24 star cloud, then afterwards M16, M17 and M18 all at once.

I found M33 in my 10x50s for the first time after looking for months using a scope. I learned then that exit pupil sometimes provides for the best view, not power.

Countless open clusters, some in areas of the sky that take on a whole new perspective when viewed at wide low-power views, like the Monoceros area, the Cygnus/Vulpecula area and Sagitarius.

Along the way, I learned star patterns much better than I ever had just using a scope. Afterwards, I could starhop navigate some areas by sight alone.

Double stars do not escape my binoculars, although at 10x the views are just the wider ones about 20" or more. But dozens upon dozens of doubles, not just the Alcor/Mizar or alpha Capricorn wide doubles.

Nebula seem to jump out in binoculars, more-so than in a scope. M27, M16, M17, M42 in the smaller binocs, but even more in larger binocs.

Of course the Milky Way, especially thru Cygnus and Perseus, in binoculars is a sight to behold, especially the densely populated rift thru Cygnus.

And back to open clusters, those in the Milky Way fields thru Auriga and Gemini, M38, M36, M37 and M35 are outstanding even in 10x binoculars. Or the fields thru the Cassiopeia / Perseus border, where near delta Cas you can see four clusters at once near M103 then just nudge little by little your way thru the area of Stock 2 and the Double Cluster, a beautiful contrasting pair.

Galaxies do not escape the 10x binoculars. I've viewed M81/M82 as a pair and even spotted M51 with 10x50s. Numerous others make it a tour thru Ursa Major, Canes Venatici and Coma Berenices. You can't pass by here without stopping to view Mel 20, Berenices Hair.

All along the way you get to see the patterns of the constellations as if you were traveling the map of the constellations in a chart book. You will pick up so much more than you ever could with a scope, you will gain a new appreciation for the patterns in the sky.

And all that with 10x50s.

So, what I use my binoculars for is to view the sky in a more intimate way, with a lot less work than any scope. Maybe the key is to just let your eyes learn how to see on a different scale.

edz


Edited by EdZ (02/13/10 07:30 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
Depth of Field and 3D or not 3D! new [Re: EdZ]
      #278014 - 12/10/04 06:36 PM

Depth of Field is the range of objects from foreground to background seen in focus at once without moving the focus dial. For instance a narrow depth of field might be all objects in focus from 30M to 50M. A wide depth of field might be all objects in focus from 15M to 75M.

This thread, once you read down into it, lays out some of the mathematics behind depth of field in binoculars. It started out with various users, including me, simply stating what we felt controlled DOF. Later on it gets into the real definition of how depth of field is determined.

Depth of Field start of thread
Read the posts by Jean Charles, Henry Link and Holger Merlitz
here are some extracts of the most important points

Quote:

I suppose that z is the distance at which objects appear sharp to the naked eye at the same time that objects at infinity.
M is the binocular magnification
d is the distance at witch the binocular is perfectly focused.
Without accommodation of the eye, we can see objects perfectly sharp at the distance d'.
By definition, the depth of field is (d d').
Now, if I suppose that the exit pupil is always larger than the eye pupil, I find the equation :

1/z = M.(1/d'-1/d)

.....So, the only optical parameter which determines depth of field is the magnification. Its influence is huge, because of the 2-power of M in the equation.
Now, why people find that binoculars with equal magnification have quite different depth of field ?
I think that the perceived depth of field in binoculars is determined by other parameters than optical ones.
JCB





Quote:

focal length has almost none impact on the DOF. It is the magnification which dominates.

In summary it seems to be that only magnification and effective exit pupil are dominating factors for DOF. Focal length has some influence but not much. However, I am not sure how well the assumptions made for these calculations are satisfied. For example, a binocular is not made of thin lenses. Only professionals may be able to figure out the validity of these assumptions, maybe with the help of ray-tracing software.

With regards,
Holger





Quote:

The results can be found with the formula I wrote in a previous post :

1/z = M.(1/d'-1/d)

Here d is infinity, z=b , M=V and d'=G.
We have therefore : b=G/V which is nearly the same as the formula on your post, in which the negligible terms have been omitted.
(For V=10 and G=100000 mm, we find b=1000 mm)
My formula is not rigorously exact, but is more general because it is also valid when the binoculars are not focused to infinity, but to the distance d.

I think it's worth doing some applications of this formula :
We suppose that the binoculars are focused to infinity, and that with naked eye we can see sharply objects without accommodation if they are 1 m away. Then DOF are :
For a 7x binocular : 49 m to infinity
For a 8x binocular : 64 m to infinity
For a 10x binocular : 100 m to infinity
For a 12x binocular : 144 m to infinity
People more than 60 years old, lacking in eye accommodation, and who have to rapidly focus between two distances (like birders), have to very carefully examine the drawbacks of high power binoculars, considering their poor depth of field.

Jean-Charles







Often associated with Depth of Field discussion is what is known as the 3D effect. So, here is some discussion about 3D, what is seen, what cannot be seen and the mathematics related to how things seem to have depth of field or appear 3D.
3D or not,3D!

Binoculars with a greater objective lens separation WILL provide more depth perception than a binocular with a lesser separation, regardless of the prism types . . . PERIOD!

the separation between objective lenses is the most important factor: a Porro 8x30 will show more 3D view than a roof 8x30.

Magnification has effect on 3D view, a greater magnification increases the compression of the fields reducing the 3D view: a roof 10x30 will show less 3D view than a roof 8x30.

Also distance has a significant impact on the so-called 3D effect;

For a binocular with objectives 150mm apart, observing two objects placed at

10 meters and 12 meters distant, the angles of view (with reference to centerline) would be 26 arcminutes and 21 arcminutes, a difference of 5 arcminutes, easily perceivably by the human eye.

100 meters and 120 meters, the angles would be 2.6 arcmin and 2.1 arcmin, only one half arcmin difference or 30 arcseconds. Already this narrow angle is beyond the perception of the human eye.

But if the objects were at
1000 meters and 1200 meters, the angles are now 0.26 arcmin and 0.21 arcmin. The difference in these two angles is merely 3 arcseconds, not only beyond the ability of the human eye, but beyond the capabilities of diffraction limited optics smaller than 46mm.

Curvature and Depth of Field
Here's a discussion why some binoculars appear to have a greater depth of field than others, even when the lens equations won't account for any difference in depth of field. As noted above, there is more to perception of depth of field than just mathematics. In this case a strong correlation is shown between the aberration Field Curvature and Depth of Field. A lens that has strong Field Curvature has a shorter focal length in the center and a longer focal length towards the edges. This has the affect of making closer objects apppear in focus if the center is focused on a distant object and the closer objects are viewed further out in the field of view. Hence the binocular has a greater depth of field, but only for nearer objects.







Edited by EdZ (02/13/10 09:30 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
BINOCULAR OBSERVING REPORTS AND TARGET LISTS new [Re: EdZ]
      #278017 - 12/10/04 06:42 PM

Binocular Observing Reports Thread Links
This link was set up so all members could add links, all in one thread, to their own observing reports. By linking here to that thread, we've got a permanent access for you to get back to the thread that shows all of our Observing Reports. We add new links to new Observing Reports in this post. Here you can access the many Observing Reports from our members.


Now that the above thread handles all the observing reports, the rest of the links here will be to Observing Lists or links for lists. edz 7-19-07


Preparing to Run the Messier Marathon?
Messier List with 20x80 binos?
here's a list of links to various Messier discussion threads


Links to Moon Maps

Observing Satellites

Check out this interesting thread
unusual use for binoculars

Links to Sattelite Observing - TiPS


DEEP SKY
Binocular Deep Sky Objects in Groups
a list of 100+ objects in about 40 groups, generally seen in binoculars in groups of two or three together. Like cluster pair M46 and M47 or galaxy three-some M65-M66-NGC3628. Some notes included giving an idea how much binocular it will take to see the targets. Also, some links to charts.


DOUBLE STARS
Binocular Doubles Seen in Pairs and Binocular Doubles within Clusters
about 30 doubles for various sizes binoculars, uniquely identified with another as a pair of doubles or apparent as a double within a cluster.


Binocular Doubles - List of about 75 Doubles showing magnitudes and separations
While the Trapezium is probably the most famous and decidely one of the most interesting multi-star systems to observe, there are many other double stars that can be observed with binoculars. This list has grown from the original list of 60 to about 80 doubles for binoculars. Some are very challenging even for large 100mm binoculars with variable power eyepieces.

Faint Binocular Doubles
a list of twenty mag 7, 8 and 9 near equal pairs, mostly for 20x80 or larger binoculars. Probably 5-7 for 15x, 12x and 10x binoculars.


How many stars should I be able to make out in the Trapezium through 11x56 obies?
For the answer to this question see the discussion at this link to the Binocular Forum
The Trapezium in Binoculars

More info on the stars in the Trapezium



Challenging Doubles for High Power Binoculars doubles mostly from 10" to 7"

Ten Binocular Doubles seen with 15x70s


COLORFUL DOUBLES

Ten Easy Colorful Double Stars see spreadsheet attachment

Common Doubles with Significant Color Contrast

THE SEARCH (for colorful doubles) GOES ON a list of 20 Doubles





LIMITING MAGNITUDE M45 - Binocular Observing Chart
See if you can observe stars down to mag12 using this chart and a table of over 250 identified stars. There are some asterisms identified on this chart. They are referred to in the post above "Binocular DSO Groups".



SURFACE BRIGHTNESS
The ability to Observe Deep Sky Objects will not always be indicated by the magnitude of the objects. For extended objects, Surface Brightness comes into play. Visual magnitude (Mv) of a deep sky "extended" object is almost always NOT the appropriate measure of how faint an extended object will appear. Determining which faint extended objects, such as galaxies, might be observed is complicated by the fact that books generally list the visual magnitude (Mv). That would be how bright the object would appear if all the light could be compressed in a small spot only 1 sq arcmin. More often, a better indicator of whether or not the object might be seen is Surface Brightness (Sb), which is usually much fainter than Mv, and even that can vary. Read this brief explanation.
See a preface on Surface Brightness in
Deep sky limits on 25x100s



Some Notes on Surface Brightness
If you took an object that is mag 8 visually (in a 1 arcmin area) and you spread the light out over an area of 10x10 arcminutes, or an area of 100 arcmin sq, then the Surface Brightness (per area) would drop by a factor of 100x from the visual magnitude. That equates to a drop of 5 magnitudes or now Sb=13. But few objects have equal brightness gradient over the full diameter. So, while we could say the entire object area aveage Surface Brightness = 13, if there is a brighter core, say Sb10, then the outer fringes might be Sb16. So usually we see only the core, and even then, that depends on the Sb of the core.



Does aperture rule in bino land?

Deep Sky Observing with 70 , 80 and 100mm Binocs

Tonight's objects with 25 x 100 IF Oberwerks

edz


Edited by EdZ (02/13/10 07:28 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
Fixed Focus Binoculars new [Re: EdZ]
      #283112 - 12/16/04 12:08 PM

Bill Cook explains the facts behind fixed focus and what value or what little value they really offer.

Fixed Focus Binoculars

Edited by EdZ (02/13/10 09:29 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
Handheld Binocular Observing new [Re: EdZ]
      #294119 - 12/29/04 07:30 AM

What are the Issues with Handheld Binoculars?
Handheld Binocular Observing Issues
not only weight, but magnification is a major issue


Resolution mounted vs handheld
This is a resolution comparison of four binoculars; a 15x70, a 12x50, a 10x50 and a 8x42. I wanted to find out how resolution changes for mounted binocular versus a braced supported binocular, braced elbows and un-braced handheld.


Small Binoculars - Resolution
here's a list of 30 small binoculars from 7x to 12x. Both the best mounted resolution and the best hand held resolution are lists. Also listed is the percent drop in resolution from mounted to handheld. It's pretty consistent. Two thirds of all binoculars tested dropped 40%-50% in resolution when hand held, and the rest were either a step above or a step below that range.


50mm Binoculars handheld vs mounted
Here's a few comparative notes out of some recent observations. Here you can compare, first the difference in what a binocular can see handheld vs mounted and second, some differences between 7x50 and 10x50. Finally you can see a difference between the two 10x50s.



How to Hand Hold a Binocular
This thread has some users notes on methods for best results

Handheld holding technique to dampen vibration?

But visit this site by forum member Stephen Tonkin for the best explanation of various hand holding techniques

How to Hand-hold a Binocular


Edited by Zdee (06/27/12 07:57 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
In Pursuit of Cheap Binoculars. What to Expect. new [Re: EdZ]
      #295344 - 12/30/04 12:07 PM

From time to time we go through this. It is generally a hard lesson for people to learn, but with few exceptions the results are usually the same. You get what you pay for.

Don't expect much from an $11 or $29 pair of binoculars when that cost is not much more than what it might really cost to just produce the objective lenses. When you think about it, binoculars are a complex instrument comprised of aligning the light path from the objective thru a pair of prisms on each side and keeping it all aligned as it passes thru two eyepieces and enters two eyes. How many of you purchase $11 eyepieces for your telescopes?

So just to remind you of the "you get what you pay for" mantra, here a a few of the recent adventures of some on this forum. Are you feeling lucky?

edz

Meade TravelView for $24.99 just remember to keep your receipt!


Barska 15x70 Nightmare a deal is not always what it seems.

good price on Meade Tarvelview not when they end up in the garbage!

Mixed opinions about these from various users More on the Meade Travelviews. Some won't go this route at all but a few people who have done so got lucky and are happy.

Meade Travelview 12x50 for $19.99 any thoughts? Most users thoughts are, if you don't expect much you won't be disappointed. As some who have gone this route point out, it's pretty much hit or miss.


Super Zoom 20-125x binoculars !

Cheap zoom binculars?
"would they be any use"?
"Oh definitely -- as paperweights, window ornaments, something to hurl at the neighbour's dog when it attempts to foul your lawn ... but not as an optical instrument". Stephen
"AND, if they very expensive ZOOM binoculars, just expect them to be expensive junk". Bill


Things to watch out for in cheap binoculars


Edited by EdZ (02/13/10 09:27 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
Testing Binoculars in the Store Before Buying new [Re: EdZ]
      #311914 - 01/15/05 09:29 PM

We got this question not long ago from an interested forum participant.

I was wondering if someone could point me to a web page that describes how to adequately test binoculars in a store before buying?

Lots of people responded. This is a collection of the advice that was given. There was other discussion.. You can see the original thread here.
Binocular Testing

There is no doubt that some things cannot be checked in a short period of time. Personally, I'm of the opinion that to check out a binocular takes weeks of use. Some things just don't come out at you until you've used it for a while. It takes quite a while to really evaluate a pair of binoculars.

If you are looking at binoculars for astronomy, then I think a respectable business would provide a means for you to somehow have a look at night.

I think the best you can do in stores is to judge the brightness and resolution and to see if the ergonomics are to your liking. A $1 bill taped to a wall 15 ft or more distant can be a way of checking resolution. Larger binoculars like 12x50 need about 25 feet, 15x70 need 60 feet and 20x80 might need 100 feet.

Look at some reflections of lights in the coatings. In the objective lens you should see several reflections and ALL of them should be color reflections, none white. Generally a white reflection indicates some uncoated surface.

Better coatings reflect less light back at you. Look for coatings that reflect the least amount of light back.

Look down inside the binocular through the objective lens. In the circular metal ring that surrounds the prism face, you should not see any prism edges exposed in better binoculars. Also you should not see any sides of the other prisms protruding into the light path. A very small clipping of the exit pupil is often seen in mid-priced binoculars.

Hold the binoculars 6 inches to a foot in front of you and look at the exit pupil, the little beam of light that comes out of the eyepieces. It should be perfectly round. If it is noticably misshapen (oval) in any way, reject it.

Look very closely at the exit pupil for any straight edges cutting into the round exit pupil. Extrememly small edges cut off of the round exit pupil won't do much harm, but in a premium binocular reject any with big edge cuts.

Once more look at the exit pupils. If you see a diamond shape around the exit pupil where the light is dimmed in the diamond shape, these are Bk7 prisms. these will probably show the dimmed view in use.

Check to see if the binoculars can come together narrow enough for the width of your eyes. Inter-pupilary distance, IPD, can range from 52mm to 78mm on some binoculars, but on others only 60mm to 72mm. If you have eyes that are set apart by only 56-58mm, you must spend the time to find a binocular that adjusts narrow enough to fit. If you are endowed with a large nose, you may need a binocular with a very wide setting.

If the binocular is to be used by children as young as 7 or 8, the IPD will need to accommodate very narrow set eyes. Of the hundreds of young kids that I've had out to view, quite a few had a problem at 59mm IPD (Orion Ultraview, Minolta Activa), most were served well with a 57mm IPD. Only very few need a binocular with IPD narrower than 55mm. Two young 4th grade girls out of 13 kids in my recent class needed less than 55mm.

Press against the eyepieces while holding them up to your eyes. If the eyepieces are loose and move in allowing you to change the focus, reject that binocular.

Make sure the right diopter has enough range to accommodate your prescription. Some binoculars do not have enough right diopter adjustment.

Look AT the edges of the body outside of the front objective lens. Look to see that both objectives are recessed from the front of the binocular by the same distance. If they are substantially different it will throw off the diopter settings when you focus and you may not get the use of all the diopter adjustment that you need for your eyes.

Focus at some distant sign. Check the image across the field of view, not only at the very center of the field, but also at the edges and midway between center and edge. How does the image look, clear and sharp or blurry? A binocular should have at least 60% to 70% of the central view clear and sharp. Any less and I would reject it.

Edge sharpness of binos is quite easy to tell when you get a pair under the stars but difficult to evaluate when viewing cityscape in the daytime. Binoculars that seem perfectly sharp in daylight can have miserable off-axis performance on the night sky, even costly premium instruments. Pinpoint star images are a much more critical test for sharpness than anything that can be done in daylight.

Shake the binocular. If you hear anything rattle, reject it.

Must you wear glasses while observing? Check to see if you can observe the entire field of view with your glasses on. If not, there is not enough eye relief.

Even non-glasses wearers should check the eye relief. If you can't see the entire field of view without glasses, pick another binocular.

Observe some very high contrast object, like a black pole against a brightly lit background, or a white post against a dark background. Do you see a lot of color fringing around the edges of the object? Do you find it objectionable?

If you don't like the way a binocular feels in your hands, it probably isn't a good choice for you no matter what the specs indicate. One of the primary advantages of binoculars over telescopes is comfort and ease of use. No matter how outstanding a binocular is optically, if it isn't comfortable for YOU, it's probably not a good choice.

Lighter is not always easier to hold for longer. After you've tried a few different binocs, you will find some that feel good and some that feel not-so-good. Not-so-good will usually get worse the more you use them.

An outstanding binocular has to be excellent optically AND ergonomically.

I've never seen ANY daytime test that gives as precise a collimation check as does checking on a star. Checking collimation at 100-200 ft. is not the same as collimation at infinity.

Certainly you can give this a try. With you eyes about an inch or two behind the binoculars, allow your eyes to let the images in each side go loose and watch to see if they come back together or merge. If collimation is really way off, you can tell in an instant.

Move every hinge and turn every dial, feel for sticking spots. Any bad humps or real sticky spots, try out another pair.

Turn the focus dial so the eyepieces are half way out. Now grab the whole eyepiece bar assembly with your fingers and try to rock it. Does it require some force to make it rock, or does it seem flimsy and rock in and out real easy? Reject flimsy.

If you don't know the differences between what the fields of view (fov) are like, then you need to try about three different sized pair with different fov. Put one edge of your view on the exact same spot for each binocular and make a note of how far across the wall it can see. Compare with the others. Every 1 field of view is 1.75 feet across at a distance of 100 feet.

You can test for pincushion distortion on a distant high-contrast sharp line, distant TV antenna or power lines or a vertical post and moving it to the edge of the field. Look for a curve in the vertical or horizontal edge. This is not necessarily bad for astronomy, but might be a reason to reject if terrestrial use is your priority.

While looking through the binocular, see what other items are for sale in the store. If the shop is full of items such as thermos flasks, thermal socks, walking boots and cheap compasses, you are probably in the wrong store.

For waterproof binoculars, it can be very useful to take along a bucket full of salty water. Ask the assistant to dunk the binocular in it for 3 minutes. Then remove it and see if there are any signs of water ingress.

Edited by EdZ (02/13/10 09:26 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
POLLS in Binocular Forum - take a poll new [Re: EdZ]
      #339414 - 02/10/05 11:52 AM

These links will take you to the several POLLS we have conducted here in the Binocular Forum. You can participate in the poll, or if you have already taken it, you can check out the results as of today. You may add comments/replies to the Poll threads.

Links to Future Polls will be added here.

edz


Poll: How many binocular forum visitors?
The binocular forum has a number of regulars. But, how many visitors do we get? Perhaps some non-members will join CN just to cast their vote. thanks, edz.
143 votes as of 6-3-08
160 votes as of 8-28-08


Poll: Binocs - Image Stabilized vs Conventional
What do you use for handheld? At what size do you use a mount?
118 votes as of 6-3-08



Poll: Did You Use our Best Of Forum Resources?
Share your opinion with us if you find the "Best Of" links useful.
32 votes as of 4-1-06
39 votes as of 4-24-07
43 votes as of 6-3-08
70 votes as of 8-28-08



Poll : Largest Handheld Binocular
98 votes as of 7-4-05
110 votes as of 3-17-06
122 votes as of 4-24-07
124 votes as of 5-29-07
141 votes as of 6-3-08
the next three sizes added together are still less than 10x50s

Poll : How Many Binoculars Do You Own?
128 votes as of 7-4-05
158 votes as of 3-17-06
173 votes as of 4-24-07
215 votes as of 5-29-07
285 votes as of 6-3-08
not surprisingly, most people own 1-2-3 or 4 pair.


Poll: What Size Binocular Do You Use Most Often?
151 votes as of 7-4-05,
the three most commonly used sizes in order are 10x50, 15x70 and 8x40/42
248 votes as of 3-17-06
261 votes as of 4-24-07
272votes as of 6-3-08
the three most commonly used sizes in order are still 10x50, 15x70 and 8x40/42


How Big are Your Eye Pupils?
71 votes as of 7-4-05
80 votes as of 3-17-06
84 votes as of 4-24-07
91 votes as of 6-3-08
most people who responded picked eye pupils 6mm or larger.
Hmmm, not the typical bell curve results we would expect to see.
Also sort of flies in the face of decades of medical studies. salt anyone.




Edited by EdZ (08/28/08 11:34 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
Binocular Vision Summation - Two Eyes vs One Eye new [Re: EdZ]
      #339415 - 02/10/05 11:53 AM

Quote:

This is your first stop for a comprehensive explanation of Binocular Summation, how binoculars, telescopes and telescope/Binoviewers all compare and the benefits that can be derived from each.
Binocular Vision Summation
This comprehensive thread includes a compilation of all I have written on Binocular Summation. In addition several noteworthy posts by other members add some imporant information on vision.

Northeastern State University College of Optometry, Tahlequah, OK
Vision Science course module by Thomas O. Salmon, OD, PhD
Vision Science Home
Salmon's Current Lectures
Old Lectures - Binocular Vision Series
Lecture 10 Binocular Summation


Predicting Binocular Visual Field Sensitivity from Monocular Visual Field Results
(Investigative Ophthalmology and Visual Science. 2000;41:2212-2221.)
2000 by The Association for Research in Vision and Ophthalmology, Inc.
Jacqueline M. Nelson-Quigg1, Kimberly Cello1 and Chris A. Johnson2
1 From the Optics and Visual Assessment Laboratory, Department of Ophthalmology, University of California, Davis; and 2 Discoveries in Sight Research Laboratories, Devers Eye Institute, Legacy Health Systems, Portland, Oregon.







Older threads that helped generate some of the information that eventually got included above.

The question gets asked, "What scope would provide the equivalent of the view thru a given size binocular?" You will find the answers here. Along with that you will find some links to some great information on the internet that will help you understand the concept of Binocular Summation. Also see the thread here at the top of the binocular forum that provides links to internet articles for more links to info on binocular summation.

Informal Shootout: 5" APO vs. Saturn III this more recent thread covers the topic in detail

Binocular Summation - Aperture Equivalency
This thread discusses what equivalent aperture would be needed in a mono view scope to produce the same amount of light and contrast as a binocular.


Binocular vs Binoviewer
in this thread the comparison takes a twist. Comparing to a binoviewer, you need to account for beam splitting and then the resultant binocular summation in the binoviewer.

This new thread Jan 2007, gives data collected from three different models binoviewers and shows how clear aperture restricts field of view. A summary is given for lowest power acceptable field of view for binoviewers and then that is also give as a binocular equivalent.
Binoviewers and Binoculars (equivalents)

Wikipedia explanations of Binocular Summation


Edited by EdZ (02/26/11 07:56 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
Binocular Photo Gallery new [Re: EdZ]
      #388157 - 03/28/05 11:05 AM

This is a collection of Binocular and Binocular Mount photos posted by members who have established a Personal Photo Gallery and have linked their photos into the Binocular Photo Gallery


Binocular Photo Gallery

The advantages of posting your photos to your own gallery and designating the gallery they appear in as the Binocular Gallery should be readily apparent. There is no memory limit to posting photos in the galleries. Once posted in your gallery you can link to your photos from anywhere without the need to ever post your photo again. Once in the gallery, you can sort all photos by several criteria. You can respond to photos with your comments. They will never get lost in an individual thread, they will always be in your own persoanl gallery.

edz


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
Binocular Deep Magnitude Observing Charts new [Re: EdZ]
      #427366 - 05/03/05 07:45 PM

These observing charts were created for studying limiting magnitude in binoculars and in small scopes. Some of the charts have from 100 to 250 stars labeled and identified with an accompanying table listing all the star magnitudes. Some charts go to mag 13.0, some only go to mag 12.5, but you will find that really goes deep for binoculars. As additional charts are developed they will be posted here.

edz

Chart of M44 to mag 13 (The Beehive)

no table of magnitudes yet for this chart


Chart of Cr399 to mag 12.5 (The Coathanger)

Table of stars with magnitude listed for this Cr399 chart


Chart of M45 to mag 13.0 (The Pleaides)

table of stars with magnitude listed for this m45 chart


Edited by EdZ (02/13/10 06:58 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
BOOKS for Binocular Observers new [Re: EdZ]
      #462329 - 06/02/05 07:46 PM

This question came up recently and as I looked back through the forum history it comes up repeatedly. This space will soon be filled with links to all the great suggestions and book reviews provided by the outstanding contribututors to the binocular forum.

edz

the newest binocular book on the market
Binocular Astronomy by Stephen Tonkin
released December 2006. Stephen is a regular in the CN binocular forum, and a presence in Astronomy, earlier I'm sure, but at least since I've been reading his stuff on the web, since 1998. This book spans the spectrum from beginner to experienced binocular user.

single best book for a binocular astronomy beginner there probably isn't just one, but this thread will help you by asking what are your needs and will highlight a few depending on what they are, learning, deep sky, science or repair.

Well then, next clear night I'll point at Sagitarius. (Where is that, exactly?) A few suggestions to help you find your way around.

Southern binocular objects... need some ideas Carsten Doehring suggests The Observers Sky Atlas by E. Karkoschka


Binocular observing books? this thread is a goldmine of contibutions by many members of the forum. Books and Charts for observing.

I would give strong recommendation to two books.
I recommend both Craig Crossen's Binocular Astronomy AND Norton's Star Atlas, not either/or.

Crossen's will give you:
a selection of objects specific to both large and small binoculars;
some very good detail localized maps, but not a full set of charts;
an outstanding explanation of the structure of the Milky Way;
a presentation of astronomy by seasons;
some excellent black and white photos close to what you see thru binoculars.

Norton's will give you:
A set of full sky charts, the Bright Sky Atlas, but no localized detail charts;
detailed lists of objects on each of those charts, some beyond binoculars;
some excellent technical explanations of the physics of optics;
some excellent technical explanations of astronomy, galaxy types, star evolution, etc.;
some detailed moon maps.



Books for Lunar Observing

and

"Modern Moon"


Star atlases suitable for binocular astronomy


Binocular Stargazing "Reynolds gives a very good overview of binocular observing" but seems to be a little light on stargazing info.

Observing Lists
"110 extraordinary objects to see with an ordinary pair of binoculars"
This link, provided by John Flannery, from the Irish Federation of Astronomical Societies (IFAS). The binocular handbook features a half-page about each object along with a chart of the field. The introduction says that you must be a member of an IFAS club, however they dropped this requirement. Feel free to get in touch with any errors or comments. Also, the handbook can be freely circulated. See comments from the author here.




Technical References

Choosing, Using & Repairing Binoculars by J. W. Seyfried, president of University Optics. Has some good, but also some outdated, information on repair maintenance and adjustment of binoculars. Has good explanations and diagrams to help the amatuer understand binocular assembly and adjustment.



BASIC OPTICS AND OPTICAL INSTRUMENTS prepared by the Naval Education and Training Development Center. recommended by William J. (Bill) Cook, Chief Opticalman, USNR-Ret., Founding Editor, Amateur Telescope Making Journal
his comments on the book,
The book has a great section on understanding basic optics principles. Other than that, the very short bino collimation section may very well be all that interests you. It is full of metal work, what kinds of greases to use for this or that, and a bunch of boilerplate that pertains to Navy instruments that haven't been made in 40 years. Please keep in mind that the collimation section deals only with instruments that are collimated with eccentric rings.


MIlitary HandBooK 141 - Optics, Vision and Optical Design
this arrangement of PDF files is hosted by the University of Arizona and represents an immense resource on Optics and Vision.


Edited by Zdee (06/25/12 09:37 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
Dark Adaptation, Eye Pupils, Lights new [Re: EdZ]
      #573393 - 08/25/05 10:50 AM

Red Light vs Green Light


Pupil Size


technical paper by C. J. R. Lord FRAS
a technical paper that plots reduction in percentage illumination as affected by eye pupil smaller than exit pupil and reduction in percentage illumination as affected by eye pupil larger than exit pupil.


technical paper on optics and vision
this in a huge reference work published by the DOD. Here is a link to the 630 page document hosted by UofA Optics Department


Poll: How Big are your Eye Pupils?


Edited by EdZ (02/13/10 06:48 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
Chromatic Aberration, Triplets, Semi-Apo, Apo new [Re: EdZ]
      #662278 - 10/29/05 11:41 AM

CHROMATIC ABERRATION (CA)

Achromats and False Color Blur Circle

The visual appearance of the ratio of color blur is low limit eye dependant. While color blur is always larger than the low limit of the eye, the resolution disks are almost always limited by the eye. Therefore in all cases we need to use the low limit of the eye for resolution.
there is a lot more visible color in a f/4 or f/6 100mm binocular than there is in a 8x40 or 10x50 and to some lesser degree even a 15x70. That's because the combination of small aperture and low power has a dramatic affect on reducing color blur.
for any given aperture, higher f# (a slower scope) provides better color correction. Most knew that. But what is not so readily known is that small apertures have very little effect on false color, or color blur as it is referred to here. An 8x40 achromat binocular has the same color error as a 120mm ED scope at 25x. The color blur in a 7x32 or 8x32 achromat, although still not apo quality, is extremely good without any further manipulation of the optics, the 7x32 being better than and the 8x40 or a 120mm ED semi-Apo scope and the 8x32 being equal. It doesn't take ED glass in the 8x40 or 7x32 to get that low color blur ratio.




The most important thing the user should understand is that it is impossible to completely eliminate CA from a lens system. It can be reduced to an almost imperceptible level, but cannot be eliminated altogether.

This is an explanation of what chromatic aberration is and how it affects the overall image
Chromatic Aberration

This explains some of the math of CA
Chromatic Aberration on planetary disks

Chromatic Abberation is one of the least worrisome aberrations. In an astro binocular, it is only present in about 1% of the objects viewed. So it should be one of the least critical aberrations on which to base a decision. Judge your choice of binocular on all the features and known aberrations that make a difference in the view 99% of the time. Honestly, the planets are not binocular targets, so the moon is the only astro target that would be a consideration for judging whether one needs to consider CA in the choices of astro binocular.

For terrestrial viewing CA becomes an important factor. CA becomes a problem in extremely bright conditions, not in low light conditions. However, there are not too many people using 15x or 16x binoculars for terra viewing.

A Table Plotting Chromatic Aberration vs Objective Size and Focal Length
see this interesting post in the refractors forum that discusses CA.. From the post...
" It illustrates the relationship of aperture and f/ratio to displayed chromatic aberration in achromatic refractors. Roughly, telescopes with similar CA ratios can be expected to display similar levels of visual CA; as CA in achromatic systems is a function of objective diameter and focal ratio.

Using this chart, one can get an idea of how another refractor will perform based on the performance of whatever model one already has. "


See this thread for
A discussion of CA in premium and well corrected optics


A discussion related to chromatic aberration in several model binoculars took place embedded in this thread.
Obie vs Fujinon CA



-------------------------------------------------------------------------------

There are two different forms of CA

Logitudinal CA is caused by the fact that, even with precisely on-axis light, in the focused image from an achromat all the wavelengths do not have the same focal length. Typically light in the image of an achromat varies from blue to red focal length by 1/1800th to 1/2000th of the focal length of the objective lens. So, for a f/4 100mm binocular, the focal length of red to blue might vary by as little as 0.2mm. That may seem inconsequential to you, but that might represent a 15-20 turn of a center focus dial on a binocular.

Light that is not focused precisely does not make the minimum sized point of light in the image. If the minimum diameter circles of light for each wavelength is at a slightly different focal length, that means when focused precisely at any one color (usually yellow) that the Airy disks of all other wavelengths (colors) have slightly larger sizes and they overlap the yellow image, forming CA in the on-axis image. This is not generally seen by the observer unless you slightly defocus the image. But rest assured it is there and it has an affect on contrast of fine detail. This may possibly be seen in the inability to bring the focus to a precisely small point of light. An achromat that is not corrected to even 1/1800th f may have a difficult time forming a precisely small image of even a moderately bright point source.


Lateral CA is caused by the fact that the light rays forming the image across the lens all have slightly different lengths to a focal plane but the focus mechanism wants to focus across a flat plane. For all the points of light in an image to be in focus at exactly the same time, our focus mechanism would be required to focus across a slightly curved image plane. That doesn't happen. Since the system is incapable of providing that precision, we see the light spread across that plane at varying amounts of out-of-focus.

If you were to draw several half inch wide concentric circles over the field of view, you would see that in the outer fov ring you see all one color, green, in the next ring in all another color, purple. The color you see is dependant on how far off-axis the image is in the plane. The further off axis, the longer the physical length of the light ray beam to the plane. The varying lengths of light rays causes each color to be out of focus more-so than some other color at different distances off axis. This form of CA is entirely due to where the light falls across the plane.

See this thread Question about CA....


-------------------------------------------------------------------------------
This comment recently generated a discussion about Achromat doublets, Triplet objectives, Semi-Apo and Apochromatic lennses, means of achieving better color correction or lower CA.

Quote:

I've learned what it means with telescopes that are Doublet and Triplet...but how is that terminology used for the 20x80 triplet bino's? are they true apo or semi-apo or something entirely different?




I answered:
I doubt you will find any binocular anywhere on the market that is a true Apo, whether it is labeled as such or not, unless possibly you are up in the range of several thousands of dollars.

The fact that it is a triplet should indeed lead to some degree of better color correction, but it is not a gaurantee. While it usually takes a triplet to make an Apochromat, triplet is no indication that any instrument, binocular or telescope, is an Apochromat. It simply means that a third element of glass is incorporated into the design to give a slightly better color correction. In a binocular, it is probably still an Achromat.

A typical Achromat has two colors corrected, usually red and blue, so their focal lengths will be within approximately 1/2000th the focal length of yellow. An instrument would need to be corrected to within 1/8000th to 1/10,000th the focal length of yellow to be considered an Apochromat.

Generally the term Semi-Apo is applied to instruments that have been corrected to within 1/4000th F. It is very likely some of the instruments on the market, both telescopes and binoculars, are not corrected to 1/4000th F, and yet are still called Semi-Apo. It could be these instruments are better than 1/2000 corrcted, perhaps 1/2500 or 1/3000. Frankly, any improvement over the level of correction of a standard achromat should be appreciated as it is not particularly easy to achieve and rather expensive to incorporate into the design. I would question if any of the triplet binoculars are reaching a level of correction to 1/4000 F.

ED Glass in Binoculars




edz


Edited by EdZ (03/26/10 01:38 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
Resolution Testing and USAF Res Charts new [Re: EdZ]
      #662351 - 10/29/05 12:27 PM

Binocular Resolution Testing Using 1951 USAF Line Pair Charts
In addition to test results for about a dozen binoculars, this thread shows some comparative results for a very good semi-apo 80mm telescope. Also included is a discussion on how to use the charts and links to web access for the charts and tables.

See the chart and the tables in my gallery here
USAF 1951 Resolution Chart and Table of Constants
It is extremely important that the chart be exactly sized.
The caution here is the user must know exactly how to size the chart.
You will find sizing notes below in this post and also in my gallery.


Source for commercially available resolution charts
Edmund Optics


Conflicting Arcsecond Test Results Explained
an excellent discussion explaining the differences in various arcsecond resolution values posted various places around the internet, and how to interpret them. This discussion is relevant to understanding how to use the USAF resolution charts and how the values determined by using them is so different than point source resolution. It explains why resolution values determined by the USAF charts are significantly closer than can be achieved observing point sources.



Understanding Resolution
a comprehensive technical report on the various criteria affecting resolution


Double Stars for Binoculars - a list of doubles for all sizes from 7x35 to 40x100
a list of double stars from which you can select observation targets providing you with good indications of the maximum visual point source resolution of your instrument.



Quote:

Lens Resolution Testing
and a link to a USAF 1951 Chart with the Table of Constants.
Chart with Table of Values


I find it interesting that few if any current web links provide ALL the information necessary to use these charts.

Using this table of values linked here which shows the constants for the Groups and Elements of the Line Pairs Chart,
the forumula is 8121 / (D x LPM) where D is the distance to your target measured in inches and LPM is the value from the Constants.
The constants are the actual number of line pairs per mm for the mimimum you can see.
For instance a 10x binocular used at a distance of 125 feet that can see line pairs in Group-1, Element2 has a value of 0.561. Therefore it's resolution is 8121/(125x12x0.561) = 9.65 arcseconds.

Line Pairs Resolution CANNOT be directly compared to point source resolution. See the forum discussion.
It is extremely important to have the target sized properly. See the discussion in the forum thread.
Binocular Resolution Testing Using 1951 USAF Line Pair Charts
included is a discussion on how to use the charts and links to web access for the charts and tables.

It is extremely important that the chart be exactly sized. As a check, the three bars and two spaces in Group-2 Element 1 should measure exactly 10mmx10mm. Both the sets of bars in G2-E2 and the solid black square top center should measure 9mmx9mm.

This page was originally accessed from
http://medfmt.8k.com/mf/resolution.html
Lens Resolution Testing by Robert Monaghan
which has posted the following notation along with the information
[My understanding is that the USAF chart etc. is in the public domain as it is a government produced chart and related documentation...]






Edited by EdZ (02/13/10 06:42 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
Limiting Magnitude and NELM new [Re: EdZ]
      #662356 - 10/29/05 12:28 PM

See also the Best of Thread on Surface brightness

Limiting Magnitude Articles and Resources


Limiting Magnitude tests on M45 - More than a dozen binocular sizes
this thread has links to charts fro M45, M44 and Cr399. it also has the record of the best observations I've recorded with dozens of binocular attempts at reaching BLM.

Bino Magnitude Efficiancy - Handheld vs. Mounted

Binoculars Limit Star Magnitude with Small Scopes Comparisons


Call for Participants in Binocular Study of M45
This post includes links to charts you can use on M45 and provides an explanation of this study.

Some results from the initial Limiting Magnitude Study and a brief summary of some of the factors that will affect LM results

First Study of Limiting Magnitude on Cr399


Limiting Magnitude in Binoculars - Lab Report by EdZ
Explains the importance of magnification to achieve limiting magnitude.

Naked Eye Limiting Magnitudes in Taurus
includes a broad selection of stars identified from mag3 to mag6.5

NELM chart Little Dipper and Polaris

NELM chart area around Sagitta, M27 and Cr399

NELM chart of Delphinus

NELM chart Circlet of Pisces

Binocular Limiting Magnitude chart to mag 13.0 in M45 - The Pleaides
includes Naked Eye Limiting Magnitudes from 2.8 up to mag 7

Binocular Limiting Magnitude chart to mag 11.0 in CR399 - The Coathanger
includes Naked Eye Limiting Magnitudes from 5.1 to 7.3

Binocular Limiting Magnitude chart to mag 12.5 in CR399 - The Coathanger
same chart as in previous, updated to include deep magnitudes for BIG binoculars 100mm and larger,
or for use in mag6+ skies where even 20x80 binoculars might be able to go deeper than mag 12.0


Limiting Magnitude chart of M44 - the Beehive magnitudes not listed but symbols provide a guide from brighest to faintest stars


This post in the binocular forum has links to the above charts, tables of star magnitudes for use with the charts and reports on some data collected with many binoculars comparing the limits of magnitude that can be reached with various sizes of binocs.
Limiting Magnitude Charts and Tables


Southern Hemisphere Several LM Charts


See these threads for discussions of Surface brightness

Does aperture rule in bino land?


Deep Sky Observing with 70 , 80 and 100mm Binocs

Tonight's objects with 25 x 100 IF Oberwerks

edz





Edited by EdZ (02/13/10 06:39 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | (show all)


Extra information
3 registered and 33 anonymous users are browsing this forum.

Moderator:  Greyhaven, Knuklhdastrnmr, WOBentley 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 148215

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics