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PostPosted: Sun Jun 30, 2013 1:49 pm 
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Location: Midlothian
HI David,
I find binocular dust caps are a bit like socks,I just cant seem to keep a hold of them! :roll:
Incidentally the dust caps are very poor on the 8X60's,the objective ones are flimsy and floppy and the eyepieces are covered by a single cap that doesn't want to stay on. :x
Ive just noticed that the Bresser 10X50's are BAK 4 while the 8X60's are BAK 7, could this be the reason that the image quality in daylight is poorer in the 8X60's?
Regards Les.


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PostPosted: Sun Jun 30, 2013 2:25 pm 
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. Hi Leslie,
the 15 x 60 Bresser that I had were very dim because the glass quality was poor and not at all transparent.
If the prisms are big enough I don't think the glass type makes a significant difference.

Apparently the barr and Stroud World War II naval binoculars etc I think made in Glasgow were known to have grey glass because they had no access to top-quality raw materials and the sands they used were from local Scottish areas.
Apparently the reason for the less than transparent glass is because of clay impurities.
The costs of removing these impurities was too high and they just made do with the raw materials they had.
it was well known in Glasgow that these binoculars had grey glass.
Schott glass was not available for obvious reasons although amazingly in World War I Zeiss binoculars were available to the British.

Incidentally, I think that Horace Dall single-handedly repaired and renovated Leitz microscope optics throughout World War II.

There are still large numbers of these binoculars around although I haven't used them even though one was in the charity shop but it looked the worse for wear so I didn't buy it.

The 7 x 50 goes for about £80-£180 depending on the quality and whether it has been serviced.
In today's terms that they are probably not very good but they are certainly built to last.

So I think the 8×60 might be dim because of the glass, but thinking about it now it is probably because your pupil size is very much smaller than 7.5 mm or even the 6 mm that the 8 x 48 suggests.
That is either at night or of course in the day.
The 10 x 50 probably has a much shorter light path going through glass than the bulky 8×60.
This may also be part of the reason.

Anyway using the 8 x 60 might be good exercise for the biceps.

Regards David


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PostPosted: Mon Jul 01, 2013 12:41 am 
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Location: Midlothian
HI David,
Thanks for the wealth of bino information. 8) .The 8X60's aren't too bad weight wise at 950g just 60g more than my beloved Clarke 7X50's which weigh in at 890g.However the Bresser 10X50's are are at a featherweight 700g in comparison.


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PostPosted: Mon Jul 01, 2013 11:34 am 
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Location: Between the New Forest and Cranborne Chase
David Frydman wrote:
. Dear Steve,
that is about what I would expect.
Do you mean 15 x 62 for the 15 x 70,
I did, yes. Thanks, and now corrected above.

Quote:
do you have an aperture for the 15 x 70 quantum?
Nope.

Quote:
The 10×41 China Marine doesn't sound very good.
Very disappointing but, apart from that, the optical quality isn't too bad.

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Best,
Steve
The Binocular Sky
Astronomers do it with Heavenly Bodies

Lots of binoculars, from 32mm to 100mm; 90mm Gregory-Maksutov, 406mm Dob


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PostPosted: Mon Jul 01, 2013 11:56 am 
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Location: Between the New Forest and Cranborne Chase
Leslie Ewan wrote:
Ive just noticed that the Bresser 10X50's are BAK 4 while the 8X60's are BAK 7, could this be the reason that the image quality in daylight is poorer in the 8X60's?
No.

Chinese BAK4 is almost exactly unlike proper (i.e. Schott) BaK4 -- it's not even a Barium Crown (which is what the BaK stands for); it's a phosphate crown with a higher bubble-count.

Chinese BAK7 is actually closer in spec to BaK4 than their BAK4 is (their BAK6 is pretty much the same as BaK4 in designation, if not in actual quality).

I suspect that you are conflating BAK7 (Chinese) with BK7 (Schott); the latter is a borosilicate crown. It has an undeservedly poor reputation, mostly due to advertising hype, perpetuated by people who ought to know better. True, the lower (than BaK4) refractive index results in some peripheral light getting lost (resulting in vignetting of the field periphery), but it also has less chromatic dispersion. This latter reason is probably why really good binoviewers like Denkmeier use BK7 (which is better for the job) instead of kow-towing to the hype for BAK4 (or BaK4). :D

In the context of this thread, you are going to get more light through an ancient single-layer coated, BK7-prismed true 10x50 than you are through one of these budget BAK4-prismed pseudo-10x50s with ineptly applied "fully multicoated" (yada yada).

Quote:
eyepieces are covered by a single cap that doesn't want to stay on.
Not a cap, but a "rainguard". Intended to do what it's name suggests. I find them useful to pop over the eyepieces when the binocular is neck-slung in order to stop beard-debris, etc. falling onto the eyepiece.

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Steve
The Binocular Sky
Astronomers do it with Heavenly Bodies

Lots of binoculars, from 32mm to 100mm; 90mm Gregory-Maksutov, 406mm Dob


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PostPosted: Mon Jul 01, 2013 7:48 pm 
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Location: Wellingborough
Dear David,

Re: Hunter Astronomical binoculars.

They are marked Japan and a serial number 3293. The only other markings are
11x80
field 4.5deg
Bak-4 prisms

They cost me £200 in 1989 - I wonder what that translates to in 2013 £s?

I tried googling Hunter binoculars but came up with only Bresser Huntsman. I also have a pair of Hunter 7-15x30 binoculars passed on to me by a family friend some years ago. They may be '60s vintage for all I know. Again, marked japan, "SMC" and a serial number. They give reasonable star images at x7 but I think light grasp is marginal for astro use.

Regards,

_________________
Brian
52.3N 0.6W
Wellingborough UK.

254mm LX90 on Superwedge, WO ZS66SD, Helios 102mm f5 on EQ1, Hunter 11x80, Pentax 10x50
ASI120MC Toucam Pros 740k/840k/900nc mono, Pentax K110D
Ro-Ro roof shed


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PostPosted: Mon Jul 01, 2013 9:25 pm 
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Location: Between the New Forest and Cranborne Chase
Was in Lidl this evening and they unexpectedly had one of the so-called 8x60s on the shelf (wasn't one there last week when I went).

* They have BK7, not BAK7 prisms (but that is the least of their problems).
* The eyepiece bridge has to be the flimsiest, rockiest one I have ever encountered.
* Collimation was noticeably out.
* Slight, but easily tolerable/acceptable pincushion distortion.
* Noticeable CA.
* Noticeable field curvature.
* Wasn't expecting to test, so didn't have my bit of graph paper that I use for aperture testing, so I couldn't do it accurately. Using the stripes on a flour packet and measuring when I got home, I get 49mm (+/- 2mm) aperture. Can anyone confirm that?

I can think of better ways to blow thirty quid on a binocular.

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Steve
The Binocular Sky
Astronomers do it with Heavenly Bodies

Lots of binoculars, from 32mm to 100mm; 90mm Gregory-Maksutov, 406mm Dob


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PostPosted: Mon Jul 01, 2013 9:28 pm 
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. Dear Brian,
the Hunter 11 x 80 has a typical specification for Japanese binoculars in the 1980s and may be 1970s with 4.5° fields.
The 20 x 80 Celestron that I have is from memory about 3.3° maybe 3.5°.
Mine is a single coated binocular but I selected it from three and took the best one.
it was not easy to find a good 20 x 80 perhaps in the late 1970s.
I used it a great deal and it gave very good images and it was reckoned that Comet Halley looked best in these binoculars rather than in the telescopes we had on L a Palma.

If you look at either the 11 x 80 or the zoom binocular do they have oval stickers either in white or yellow. They may be worn or you might still be able to read what it says.
If you can tell me what it says if they are there I may be able to work out the date of manufacture.

£200 in 1989 might be £500 today?

SMC means super multicoated and was used by Pentax for their lenses.
I don't know if another firm copied this.
Anyway Pentax farmed out their binoculars and they were made by many small Japanese optical houses, some are exceedingly good such as the very early 8×24 angular black binocular which has the best focusing on any binoculars I've ever used.
If it wasn't for their lack of nitrogen purging I would say they are as good as the very best binocular at that time.

Is the zoom binocular single blue coated or perhaps green or other colour multicoated?
if it is blue coated then the SMC is maybe wishful thinking.

Best regards David


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PostPosted: Mon Jul 01, 2013 9:48 pm 
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Brian,

It seems that £200 in 1989 is now worth about £425.

Pentax introduced SMC or super multi coating in 1971 for their M 42 screw mount lenses.

Regards David


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PostPosted: Tue Jul 02, 2013 9:07 pm 
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Location: Midlothian
HI All,
Its obvious that these £30 instruments are not going to do well under scrutiny of thorough bench tests.Binoculars having such low power means within reason a small level of optical defects aren't so important than in the higher power telescopes.As long as they gather a lot of light and show some clusters and faint fuzzies Im pretty tolerant of of a few small niggles. 8)
The big test is the field test,cloud has been a problem here but Ive got my 8X60's on my tripod ready for the next clear night hopefully this year!
Regards Les.


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Bresser 8X60's On Tripod 02.07.13.jpg
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PostPosted: Tue Jul 02, 2013 9:40 pm 
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. Dear Les,
they look good.
As long as they are collimated they should be useful.
I agree that some amount of chromatic aberration is quite tolerable as is a curved field.
In fact some of the most expensive Zeiss binoculars have curved fields. although younger eyes have an easier task of correcting for the curved field.

It would seem that they are may be fragile so that if they are in collimation now it would be wise not to knock them.
So with care they should last.

Hope the clouds clear.

Regards David


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PostPosted: Wed Jul 03, 2013 5:39 pm 
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Hunter 7-15x30

Dear David,

the optics reflect a deep blue/mauve colouration. On the prism housings it states "triple tested" and "fully coated" (left side) and "7-15x30mm", "Zoom" and "300ft at 1000yds at 7x" (right side). Centre focusing is via a left-to-right slider bar, not a wheel. The legend "RTC" is moulded into this bar.

At the end of the centre bar, where a tripod mounting plate can sometimes be fixed is a non-removable plastic disc with the legend "SMC" "japan" and "C01773". No oval stickers ( like the ones that say "passed" ) I'm afraid ,

Regards,

_________________
Brian
52.3N 0.6W
Wellingborough UK.

254mm LX90 on Superwedge, WO ZS66SD, Helios 102mm f5 on EQ1, Hunter 11x80, Pentax 10x50
ASI120MC Toucam Pros 740k/840k/900nc mono, Pentax K110D
Ro-Ro roof shed


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PostPosted: Wed Jul 03, 2013 6:24 pm 
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. Hi Brian,
it could be single coated possibly an early double coat, I'm not sure.

It should have on both the zoom binocular and the 11×80 a couple of engravings looking like JE and JB.
These may be difficult to see but should be there. maybe black-on-black .

Can you look at either binocular and tell me if you find these and what the markings are.
One is for the body manufacturer I think and the other maybe for the over all manufacturer.

These may tie-up with some of the information you gave me.

There were also silver stickers but as none of them are there I can give an accurate date.

Regards David

Could RTC be actually rapid focus control? I cannot think what it means.


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PostPosted: Wed Jul 03, 2013 6:55 pm 
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Leslie Ewan wrote:
HI All,
Its obvious that these £30 instruments are not going to do well under scrutiny of thorough bench tests.
Indeed not -- for the price of half a half-way-decent-ish astronomical eyepiece, exactly what is it reasonable to expect from a binocular (2 eyepieces, 2 objectives, two prism assemblies, and associated tubing). However, I still think it's valid for people to know exactly what they are getting, especially as a lot of the cost-cutting is going to be on Quality Control (i.e. the customer becomes the QC department).

I don't expect any binocular for under several hundred quid to be CA free and have a flat field. However, the stupidly rocky eyepiece bridge is a design problem, and the lack of collimation (and propensity of this class of binocular to lose collimation) is something people should be aware of (IMO, of course).

As I hope I indicated, the BK7 prisms are a minor issue -- in fact, for me they aren't one.

The thing that is, for me, a major issue is the reduced effective aperture. Quite simply, claiming something has an aperture that is 20%-ish greater than it actually has is fraud. It may be very common, but it is still fraud.

And, for significantly less than £30, you can get a reasonable 2nd hand (aka used, aka "pre-loved") well-constructed, lighter, true 50mm binocular which is a lot more robust and which will probably last a lot longer -- that is my beef with these budget imports.

_________________
Best,
Steve
The Binocular Sky
Astronomers do it with Heavenly Bodies

Lots of binoculars, from 32mm to 100mm; 90mm Gregory-Maksutov, 406mm Dob


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PostPosted: Wed Jul 03, 2013 8:43 pm 
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Location: Wellingborough
Hunter 7-15x35 binoculars.

Dear David,

I could find no JE/JB type makings on either binocular I'm afraid. I'm assuming they would be 1-2mm sized lettering, there's definitely nothing of that sort to be seen.

Anyhow, I've been Googling again and found some similar binoculars. It appears that "RTC" represents the manufacturer/distributor and there appears to be some connection with a US Company "JCPenney" who may not now exist.

This is a link to apparently a currently available 7-28x50 which in every other respect looks identical to the build of my 7-15x35:
http://www.beercityaudio.com/index.php/ ... -zoom.html

Out of interest, this link is to a 1950's 7x50 marine binocular with the same focusing mechanism:
http://www.worthpoint.com/worthopedia/1 ... -102350821

and this is a JCPenney 10x50 marine binocular on E-bay:
http://www.ebay.com/itm/ws/eBayISAPI.dl ... rid=229466

Regards,

_________________
Brian
52.3N 0.6W
Wellingborough UK.

254mm LX90 on Superwedge, WO ZS66SD, Helios 102mm f5 on EQ1, Hunter 11x80, Pentax 10x50
ASI120MC Toucam Pros 740k/840k/900nc mono, Pentax K110D
Ro-Ro roof shed


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