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Just feeling my very old oats (1 Viewer)

WJC

WJC

Well-known member
Frequently, I see folks raving about this or that binoculars excellent collimation. Tonight, I came across a post on Cloudy Nights wherein the poster was declaring that a certain binocular had "absolutely zero collimation error."

Therefore, I would like to declare that having collimated thousands of binoculars and having read numerous scientific and technical papers on the subject:

THERE HAS NEVER BEEN A BINOCULAR MADE THAT HAS HAD ZERO COLLIMATION ERROR! NEVER! Nor, can there be.

Tiny? Yes.
Imperceptible? Yes.
Inconsequential? Yes.
ZERO? I have some oceanfront real estate to sell just north west of Wichita, Kansas for sale at a good price.

I try very hard to keep from spouting more that I know. I don't always succeed, but I do try. I wish others would try as hard. :cat:

Bill
 
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It's kinda like resolution - if they out-resolve my eyes, do I care [or need to care] what the actual resolution is?

Of course, Bill and Henry would say ''yes'', being technicians and aiming for the ideal, while the rest of us are just looking for a great view and any technical limitations, if not visible, are essentially moot.
 
james holdsworth said:
It's kinda like resolution - if they out-resolve my eyes, do I care [or need to care] what the actual resolution is?

Of course, Bill and Henry would say ''yes'', being technicians and aiming for the ideal, while the rest of us are just looking for a great view and any technical limitations, if not visible, are essentially moot.
Click to expand...

No, James. I wouldn't say it is. I would just say, "CALL IT WHAT IT IS," that the novice not be misled. I get wrapped around the axle when some screw-tweaker claims to have "collimated" his binocular, when I know he hasn't. Conditional alignment will serve most people quite well and I've stopped the process there a number of times. I just didn't CALL IT "collimation," ona-counta ... it ain't. :cat:

Bill
 
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Speaking of CN, & collimation like the world has nevah seen, how do you feel about fov being determined by various stars w/known degrees of separation Vs. the other end of the spectrum; say 100' in the backyard?
 
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The FOV at 100ft may be slightly different to that at stellar distances, by varying amounts.
This depends on the binocular and possibly the observer. And the observer's eye prescription.
Also when a star is at the field stop may be difficult to determine.
Equally a measure in the daytime may be difficult to determine.
Also we have day and night conditions.
Plus exact eye positioning axially and slightly off centre, and exactly correct IPD or slightly wrong IPD where the field using both barrels may be a little wider than a single barrel.
Also two barrel FOV is often slightly different to one barrel.
In other words, exact FOV is difficult to determine but can be given an estimated error.

Star positions and separations using spherical geometry are different to those measured on screen, even with fairly accurate sky programmes.
Using normal star maps is useless as the errors of flat maps are too great and depend on the projection used.

And where is the 100 ft measured?
Centrally or at the ends of a flat tape?
And how accurate is the tape measure?
We have flat plane measure and angular measure.
These are different for wide angle binoculars.

Well, you did ask.
 
Yes I did and thanks for the response. Let's say vision is 20/20 and you look w/dominate eye through only one barrel. At 8x movement of the earth is slight and easily compensated for by a fluid head mount.

Instead of a tape in the yard I have centered the glass and 100' from there I placed two dowel pins at equal distance at the edge of fov. From that point I measure w/100' steel tape.

Would more error be likely w/one or the other methods or is it merely six of one, half a dozen of the other?
 
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Binastro said:
The FOV at 100ft may be slightly different to that at stellar distances, by varying amounts.
This depends on the binocular and possibly the observer. And the observer's eye prescription.
Also when a star is at the field stop may be difficult to determine.
Equally a measure in the daytime may be difficult to determine.
Also we have day and night conditions.
Plus exact eye positioning axially and slightly off centre, and exactly correct IPD or slightly wrong IPD where the field using both barrels may be a little wider than a single barrel.
Also two barrel FOV is often slightly different to one barrel.
In other words, exact FOV is difficult to determine but can be given an estimated error.

Star positions and separations using spherical geometry are different to those measured on screen, even with fairly accurate sky programmes.
Using normal star maps is useless as the errors of flat maps are too great and depend on the projection used.

And where is the 100 ft measured?
Centrally or at the ends of a flat tape?
And how accurate is the tape measure?
We have flat plane measure and angular measure.
These are different for wide angle binoculars.

Well, you did ask.
Click to expand...

:t::t::t:

Lee
 
With star measures.
How bright is the star?
Sirius will be seen just past the field stop. I try to use 2nd magnitude stars.
The star separations should be accurate to one part in a thousand.
I only know perhaps a dozen accurate separations, some to 1 part in 10,000.
I cannot be bothered to use spherical geometry each time.

The Earth moves around at 1 deg every 4 minutes, but is not relevant as one is seeing two stars at the same time.
Hand held binoculars have greater fields than tripod mounted ones because the observer is alive and not still.

FOV, magnification and binocular size are dependent on observer.

Weight is the most accurate, but varies with Earth position.
Binocular tolerances also make no two binoculars identical.

Published specs are often fiction.

I can get field sizes to 1% using stars, at best 0.5%.

I don't know about linear fields as they are of little interest to me.

Anyway one cannot exactly equate angular measures to linear measures.
 
Steel tapes have a standard error.
Also they lengthen by 1 part in 10,000 for every 15 degree F above 68 degrees.
They have to be corrected for sag.

Arizona is hot, but has good skies, which I unfortunately have not seen.

Invar tapes are better.

One should cover the unused binocular barrel with the cap.

If the dowels are at 100ft, the centre point is less than 100ft.
If the dowels are 1 inch thick, that is 1 part in 1,200.
 
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Binastro said:
Published specs are often fiction.
Click to expand...

Like, maybe the Fuji ad attached, wherein the copy writer didn't know his REAL field from his APPARENT field. :cat:

Bill
 

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I think that careful measurement at 100ft will give 1% accuracy.

However, I think that the linear measure at 100ft will usually differ from a linear measure at 1000yds.

The star measures at night using a 5mm eye pupil will differ to using a 2mm eye pupil with say glitter balls very distant in the daytime, or in fact stopping one's eye to 2mm at night.

P.S.
With an 8 degree field binocular the distance to the centre point with edge dowels at 100ft is 99.75ft.

With a 12 degree binocular the distance to the centre point is 99.45ft.

With many binoculars the star images near the field stop are such a mess that one cannot be sure what one is measuring.
I don't know how this very messed up edge relates to daytime measures with dowels at the field edge.

When measuring two binoculars at the same time, say an old heavy Swift 8.5x44 with a later HR/5 8.5x44 the accuracy is greater than the intrinsic values. The difference in field size is more accurate than the measured full field size. Say in arcminutes.

P.P.S.
I made a mistake. Arkansas is only about 93F in summer.
Arizona 103F. Sometimes hotter.
So the steel tape will lengthen less.
 
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Is it possible, if improbable, that there can be zero error by chance? Not that such a possibility would support a claim of zero error, but I'm just curious
 
St. Elmo said:
Is it possible, if improbable, that there can be zero error by chance? Not that such a possibility would support a claim of zero error, but I'm just curious
Click to expand...

And THAT is a very sensible query, presented in a sensible fashion.

IF it were possible, it would change during the next few seconds due to changes in temperature, barometric pressure, humidity, etc.

Let’s have an example: Start with an 8 ½” by 11” sheet of paper. Draw a line at each end. Now, draw a line half way between the first and second line, then between the first and third, then between the first and fourth. Before too long (halving the distance each time) you would not be able to see the pencil move, even though an electron microscope would show the closest lines separated by a football field. Then if you kept at the boondoggle for a few days ... there would STILL be a difference!

The question is: When is good enough ... good enough?

It goes back to my original argument. Some see it as nothing more than semantics. For the most part it is. I just don’t want the non-ending bad information fostered by the unknowing to continue on unabated. It matters, or at least it SHOULD. :cat:

Bill
 
Binastro said:
Arkansas is only about 93F in summer.
Arizona 103F. Sometimes hotter.
So the steel tape will lengthen less.
Click to expand...

Yet, one must factor the dry Arizona heat against the humid Arkansas heat.

Either way if under a SunSetter retractable awning the temperature would be about 20* COUP-lah.
 
Nixterdemus said:
Yet, one must factor the dry Arizona heat against the humid Arkansas heat.

Either way if under a SunSetter retractable awning the temperature would be about 20* COUP-lah.
Click to expand...

When it gets so hot ... it doesn't matter. I have lived through one without AC or a fan and the other WITH both.

I was in Phoenix 3 weeks ago. A tire on my daughters popped because of the heat, alone.

Bill
 
Are you sure that her tire wasn't underinflated?

We've had an unusually cool and wet summer save a few days stretch here and there. Yesterday it didn't break the 80's.

ETA: I bought a LW 22x80 bin online. They asked if I was going to use it to look at the stars or terrestrial. I replied the latter. Later, I wondered about the inquiry.

It arrived and one tube reeked of curing epoxy. After a couple of days the skies cleared and I managed, through the new bin, to double the amount of stars in the sky.

The replacement did not smell and it was collimated within specifications.
 
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