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Old Wednesday 8th June 2016, 00:18   #26
Rathaus
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Ed,

There is also a code written in black pen on the front plate and on the eye piece structure as seen here. DN22 7GF 19. Any idea what this might refer to?

Rathaus
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Old Wednesday 8th June 2016, 14:36   #27
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Hi Rathaus,
The code is the address In Doncaster of the binocular maker. No, actually the binocular previous owner.

It seems to be half a mile from Botany Bay.

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Old Wednesday 8th June 2016, 19:53   #28
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Quote:
Originally Posted by Rathaus View Post
...
Re The single thread test - I look for a single thread from a spider or caterpillar a few inches long (6-12inches...sometimes longer) which is usually stretched between bark or twigs. The best thread is Very fine/barely perceptible. Sometimes it's also a waving piece of thread. Shaded or sunny, this is the most ruthless test I've come up with so far for binoculars. I usually view from 30-40 feet away. Some of my sharpest binoculars can struggle with the thread test. It's almost spooky and ghost like when the thread appears in some binoculars and not others.

I walked up to the piece of thread I was viewing yesterday to check it out, and it took me a minute or so to find it from just 12inches away with the naked eye. I knew where it was but still couldnt locate it for some time. Incredibly difficult to see. A couple of the binoculars gave me a better view from 30-40 feet away.

Cheers

Rathaus
Very interesting! Did you make that procedure up yourself? The reason I ask is that, depending on how one defines acuity, the limit of human capability is about 0.5 arc seconds, which is well below commonly accepted grating acuity. See Wiki article, where this is discussed towards the end of the article and is doubtless based on the seminal work of Hecht & Mintz (1939) that I've attached.* So far, you are the first I've seen to incorporate this into binocular instrument evaluation. Congrats!

* Some astronomers and opticians on BF take issue with the article claiming that Hecht was old fashioned, or unfamiliar with classical optics, etc. However from his NAS obituary:
Quote:
In 1941, Hecht was awarded the Frederick Ives Medal of the Optical Society of America. He was elected to the National Academy of Sciences in 1944. A director-at-large of the Optical Society of America, he also served on the editorial boards of the Journal of the Optical Society, the Biological Bulletin, and Documenta Ophthalmologica.
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Old Wednesday 8th June 2016, 21:40   #29
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Hi Ed.
I read the Visibility of single lines article. Thanks.

I don't think astronomers would disagree as it is astronomers who confirm the findings by observation.

However, I am not sure how accurately it tests binoculars optics, as poorer optics could expand wires to larger apparent sizes than top quality optics.
I am not sure of this, but maybe Typo commented on this.

Also illumination of beads on wires by sunliight will render them visible even when much less than 0.5 arcsecond wire diameter.

This is also why I object when people here talk of Dawes limits, when it is not Dawes limits they are seeing.
And the fact that resolution limits vary from 0.5 arcseconds to several arc minutes just shows how one cannot just talk about resolution without saying what you are measuring.

It is like pairs of binoculars, sets of binoculars compared to a binocular.
I am probably too pedantic as these terms are used in the venacular. I sometimes talk of binoculars myself when I mean binocular, but I try to be consistent.
Same with Dawes limit. Poor Rev. Dawes will be turning in his grave. He was not in the best of health when he actually made his observations. Good thing he didn't read this site.
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Old Wednesday 8th June 2016, 23:05   #30
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Originally Posted by elkcub View Post
Very interesting! Did you make that procedure up yourself? The reason I ask is that, depending on how one defines acuity, the limit of human capability is about 0.5 arc seconds, which is well below commonly accepted grating acuity. See Wiki article, where this is discussed towards the end of the article and is doubtless based on the seminal work of Hecht & Mintz (1939) that I've attached.* So far, you are the first I've seen to incorporate this into binocular instrument evaluation. Congrats!

* Some astronomers and opticians on BF take issue with the article claiming that Hecht was old fashioned, or unfamiliar with classical optics, etc. However from his NAS obituary:
Cheers for that. Yes I did come up with it myself...I would very much like to say that I came up with this idea following profound contemplation whilst utilising a deep understanding of physics and mathematics.....but, alas, I just stumbled upon it one day when an incredibly thin piece of thread was appearing and disappearing in my view depending on binoculars used - I never read about it. However, at the time I was quite excited - I was fully aware that a significant optical event was taking place. I look forward to reading the article. My thread viewing has become like an 'astronomy on the ground' type of viewing for me now.
One of the difficulties, obviously, is actually finding (seeing) an appropriate piece of thread in the first place! It took me half an hour yesterday to find one. Also, sometimes I trace a longer easier well lit piece of thread back to a shaded section where the thread disappears and use that section as my target....or a tendril from a larger web.
I do not profess to know or fully understand what is going on during this process but I have never come up with a test which can so ruthlessly seperate binoculars. Sure, It may not mean one binocular is 'better' than the other, but it does indeed seperate binoculars.

Cheers,

Rathaus

Last edited by Rathaus : Wednesday 8th June 2016 at 23:32.
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Old Wednesday 8th June 2016, 23:08   #31
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Hi Rathaus,
The code is the address In Doncaster of the binocular maker. No, actually the binocular previous owner.

It seems to be half a mile from Botany Bay.
Oh dear. Is it specifically revealing the address? If that is the case I will delete it. I was hoping it was a code to a bloated Swiss bank account
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Old Thursday 9th June 2016, 02:31   #32
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There is also a code written in black pen on the front plate and on the eye piece structure as seen here.

Ps: perhaps not required, but I've deleted the address codes to ensure online privacy for the previous owner. I'd personally rather that our roles were reversed.

Last edited by Rathaus : Thursday 9th June 2016 at 02:45.
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Old Thursday 9th June 2016, 02:44   #33
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Admin,

Could you please delete my post #26. I posted it not knowing that the code written on the binoculars reveals the private address of the previous owner.
I attempted to delete too many times and it won't work for me.

Many thanks.

Rathaus

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Old Thursday 9th June 2016, 14:14   #34
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Hi Rathaus,
The fact that you cannot see fine thread with unaided eyes close is probably because your eyes don't achieve exact focus.
With a binocular at a distance exact focus is easy. With our unaided eyes we don't have control.
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Old Friday 10th June 2016, 01:27   #35
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Quote:
Originally Posted by Binastro View Post
Hi Ed.
I read the Visibility of single lines article. Thanks.

I don't think astronomers would disagree as it is astronomers who confirm the findings by observation.

However, I am not sure how accurately it tests binoculars optics, as poorer optics could expand wires to larger apparent sizes than top quality optics.
I am not sure of this, but maybe Typo commented on this.

Also illumination of beads on wires by sunliight will render them visible even when much less than 0.5 arcsecond wire diameter.

This is also why I object when people here talk of Dawes limits, when it is not Dawes limits they are seeing.
And the fact that resolution limits vary from 0.5 arcseconds to several arc minutes just shows how one cannot just talk about resolution without saying what you are measuring.

It is like pairs of binoculars, sets of binoculars compared to a binocular.
I am probably too pedantic as these terms are used in the venacular. I sometimes talk of binoculars myself when I mean binocular, but I try to be consistent.
Same with Dawes limit. Poor Rev. Dawes will be turning in his grave. He was not in the best of health when he actually made his observations. Good thing he didn't read this site.
David,

Yeah, it always seemed to me that the word binoculars is curiously redundant. Bicycles, for example, refers to more than one bicycle; so why wouldn't binoculars refer to more than one binocular? I guess folks who use the word "maths" know how to explain it, ... I don't.

Ed
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Old Friday 10th June 2016, 13:41   #36
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Ed,
Too true.
I did study Maths and folks here don't know what Math is.
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Old Friday 10th June 2016, 15:26   #37
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David,

Yeah, it always seemed to me that the word binoculars is curiously redundant. Bicycles, for example, refers to more than one bicycle; so why wouldn't binoculars refer to more than one binocular? I guess folks who use the word "maths" know how to explain it, ... I don't.

Ed
Yo, Eddie:

I threatened you with being back on the 10th!

The VERY LAST page in my book will have two photos. The one on the left will be of a binocular; the one on the right will be a PAIR of binoculars.

Bill
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Old Friday 10th June 2016, 15:36   #38
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I try to use the singular form, especially when discussing something a singular as my HR/5!

Bob
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Old Friday 10th June 2016, 19:52   #39
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Yo, Eddie:

I threatened you with being back on the 10th!

The VERY LAST page in my book will have two photos. The one on the left will be of a binocular; the one on the right will be a PAIR of binoculars.

Bill
Welcome home, Billie boy.

Cool. Will that be a matched pair?

Ed
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Old Friday 10th June 2016, 19:58   #40
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Ed,
Too true.
I did study Maths and folks here don't know what Math is.
I can extend math to mathematics; what do your guys get, mathsematics? It figures not.
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Old Friday 10th June 2016, 21:16   #41
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Math sounds really alien to us.

We had a great BT ad.
Describing how well the son had done.
Ooh. He got an ology.
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Old Monday 8th August 2016, 15:11   #42
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Mint boxed HR5

I just picked up one these, mint condition, boxed. Lovely binocular, I had one before and sold it as I found my older Gold Band HR Audubon to give a more relaxing view, despite it being bulkier and heavier than the HR5.When comparing with my Gold Band HR, the passage of time has not really altered my initial feelings, i'm pleased to have this, but for some reason find the image from the older model more relaxing, the colors just seem a bit better and the viewing easier.

I still couldn't resist this one for my collection
https://www.flickr.com/photos/[email protected]/
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Old Monday 8th August 2016, 21:15   #43
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I just picked up one these, mint condition, boxed. Lovely binocular, I had one before and sold it as I found my older Gold Band HR Audubon to give a more relaxing view, despite it being bulkier and heavier than the HR5.When comparing with my Gold Band HR, the passage of time has not really altered my initial feelings, i'm pleased to have this, but for some reason find the image from the older model more relaxing, the colors just seem a bit better and the viewing easier.

I still couldn't resist this one for my collection
https://www.flickr.com/photos/[email protected]/
Nice find, Ben.

I have two of these. The latest one I couldn't resist buying a few months ago in mint condition. I don't know how many surfaces are multi-coated, but for some reason I prefer its image and ease of view to later HR/5s that were fully multi-coated. Type 2 or 3 Audubons, though, would be a step too far back in time for me.

Very nice collection, and nicely photographed.

Ed

Incidentally, your new find was the Pyser version sold in the UK and Europe, just so you know.
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Old Tuesday 9th August 2016, 10:10   #44
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Hi Ed,

Many thanks for the info. This week I bought a Swift I have not seen before, not arrived yet so cant take a photo, but I will post the sellers photos, it is called the Swift Vulcan 7x35 poro, would you know anything about this model?

Ben
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