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B&W Nano coated 46mm clear filters on Zeiss 8x42HT

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Old Sunday 13th October 2019, 19:04   #26
Robert Moore
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Look how nice the coatings are on this Astro-Physics Fast Max 180. It’s like the glass is invisible.
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Old Sunday 13th October 2019, 19:18   #27
Robert Moore
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Beautiful telescope. I think only 7 of these were made. I was on a waiting list from the 90s and got a call a few years ago for this scope.
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Old Sunday 13th October 2019, 20:14   #28
Binastro
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That is a beautiful telescope, Robert.
I wasn't aware of these, although there are cheaper commercial Maksutov Newtonians.

A friend has a 7 inch Astrophysics refractor and there was one in Finland at a town observatory.

I ordered a custom British 12 inch Maksutov in the early 1970s.
The optics were completed but the corrector plate split in two on the makers work bench.
He gave up making optics and authoured many fine books.

I refused to take back the money that I had paid up front, and a 12.5 inch f/3.5 f/14.7 windowed thin edge mirror Dall Kirkham was made instead. It took three years and involved about four of the best U.K. opticians.
I was told that one quadrant was not up to their standards, but I never noticed anything amiss in use up to 700x and more.
The optical window cost more than the primary.
This took any power up to 1100x. Uncoated, but I never saw ghosts for some reason.

The 20.5 inch f/3.9 Newtonian primary made for me by one of these workers was 1/20th wave. He is one of the two top U.K. professionals at the time. They made scopes up to 4 metre aperture.

I think that some people using Herschel wedges also use filters also to reduce the heat and radiation. I have never used one.

I only project the Sun with refractors or use the PST at 32x with over 2,000 days drawings. I only observe casually nowadays.
I used to submit planetary, solar and comet observations etc.
I still record NLCs and any fortuitous observations.

This evening there was a very colourful red cloud sunset. These have been reported recently as of volcanic or fire origins, possibly worldwide.
The last few days have been rainy.

Regards,
B.
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Old Sunday 13th October 2019, 20:42   #29
Robert Moore
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I don’t observe as much as I should. I get lazy and don’t want to mess with it all and that’s one reason I love binoculars. I use to have the big Nikon 20x120III and had them on a geared head Linholf tripod and they were fantastic. I would like to get another large binocular at some point. That 20” scope sounds nice. I use to have a 20” obsession telescope and really enjoyed those lovely globular cluster views.
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Old Monday 14th October 2019, 01:16   #30
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Robert:
Now I see, you are an astro viewer, a very different user than a common birder, terrestrial user.

Go ahead, and enjoy your filters, you may like how they help your viewing.

Jerry
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Old Monday 14th October 2019, 23:53   #31
GoldenBear
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I have the exact same filters on my HT 8x42's and love them. I had them for a few months and so far have had no issues with condensation or fogging. I was more concerned that the flat filter surface may cause more glare or flares under certain light angles, but there's been no impact whatsoever.

Absolutely optically invisible as far as I can tell, and I compared them extensively in the field and against resolution charts. Much easier to clean the flat filter surface (especially with B&W's excellent nano coating). They also negate the need for objective covers (although I did but a pair of inexpensive pinch style caps the fit the filters for transport and travel).

Another nice advantage to the B&W fllter compared to most is that the metal frame is brass rather than aluminum which helps reduce he chance of seizing.

With regard to any effect on the image, if anything, when I first put them on I would swear the field curvature of the image became slightly less noticeable. No doubt it isn't optically possible for the filters to change the image in this way, but it sure seemed like it did to me eye.
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Old Tuesday 15th October 2019, 02:55   #32
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Glad to hear someone else is using them. I was checking last night on the moon and the moon was extremely bright and I could not detect and ghosting or reflections of any kind. I found this pair of HT in new condition and I wanted to keep them that way. That is why I wanted to try the filters and see how they performed. To be honest I wasn’t expecting them to be this good. Like you I can see no image degradation whatsoever. At 8x I wasn’t expecting any softening to the image but I thought I might get some glare or ghosting and I just am not seeing any.
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Old Tuesday 15th October 2019, 10:08   #33
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GoldenBear,

I am not so sure that a flat glass filter cannot affect rays of light coming at an angle into the optical system.
Whether this can lessen field curvature, I don't know.

I have noticed a change in focus with a 200mm camera lens, Tamron maybe, through a good single plate glass window.
I think that here there might have been some curvature in the window, but I don't see how. It could be a pressure difference, but this was not double glazing.

Regards,
B.
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Old Tuesday 15th October 2019, 11:19   #34
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With reference to filters in general.
It seems that resin filters reduce the resolution of lenses, when top quality glass filters don't.

I know that the eclipse glasses generally available reduce resolution compared to high quality glass filters, seen with safe filters and unaided eyes on sunspots.

The glass stacks in front of digital camera sensors vary from about 1mm Leica to 4mm. These different thicknesses affect lens resolution and general optical characteristics.
How good lenses are on digital cameras varies with different camera bodies.

High resolution lenses have to be designed for the whole system.

I think I recall that aero lenses were computed to include the glass register plates that held the film flat.

B.

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Old Tuesday 15th October 2019, 12:58   #35
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Considering the efforts of binocular producers to supply binoculars with hard, water- en dust repellent coatings the use of filters for protection purposes seem unnessecary to me. I never have had the temptation to use one.
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Old Tuesday 15th October 2019, 14:02   #36
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Sand / silica has a hardness of 6-7 on the Mohs' Scale, equivalent to quartz, propelled by the wind sand will chip or scratch objective lenses.

I have a Zeiss Conquest HD 8x32 with a sand chipped objective not that it interferes with the view, just the aesthetics.

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Old Tuesday 15th October 2019, 14:38   #37
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I got about twenty 4 inch f/1.8 lenses as a job lot.
Only two were usable.
The others all had sand blasted front elements, some almost opaque, because the techs forgot to put the front filters on.
They were used underneath aircraft for photography.

I also had a Zeiss 10x40 Classic rubber coated binocular.
The lenses were destroyed by the user who may have cleaned them repeatedly with a scarf on his sandy beach.
The binocular came from a seaside town.
I found it hard to believe anybody would treat optics like this.

But personally, I have almost never used filters even with my Minolta cameras on the beach.
My lenses and cameras still look almost new after nearly 50 years.
The cameras always had an ever ready case that took about one second to drop the front and take a photo, with the close fitting rubber double grip front caps dropping into the front of the case.

B.
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Old Tuesday 15th October 2019, 16:45   #38
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Originally Posted by Binastro View Post
GoldenBear,

I am not so sure that a flat glass filter cannot affect rays of light coming at an angle into the optical system.
Whether this can lessen field curvature, I don't know.

I have noticed a change in focus with a 200mm camera lens, Tamron maybe, through a good single plate glass window.
I think that here there might have been some curvature in the window, but I don't see how. It could be a pressure difference, but this was not double glazing.

Regards,
B.
I don't know how a flat filter would affect field curvature but a flat filter will _definitely_ affect the focal point. The focus adjustment will be need to be different for a lens when used with and without filters at a given distance.

--AP
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Old Tuesday 15th October 2019, 17:01   #39
Alexis Powell
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Originally Posted by Binastro View Post
I got about twenty 4 inch f/1.8 lenses as a job lot.
Only two were usable.
The others all had sand blasted front elements, some almost opaque, because the techs forgot to put the front filters on.
They were used underneath aircraft for photography.

I also had a Zeiss 10x40 Classic rubber coated binocular.
The lenses were destroyed by the user who may have cleaned them repeatedly with a scarf on his sandy beach.
The binocular came from a seaside town.
I found it hard to believe anybody would treat optics like this.

But personally, I have almost never used filters even with my Minolta cameras on the beach.
My lenses and cameras still look almost new after nearly 50 years.
The cameras always had an ever ready case that took about one second to drop the front and take a photo, with the close fitting rubber double grip front caps dropping into the front of the case.

B.
I've never had a problem with blowing sand scratching camera lenses despite much use in blowing sand in the deserts of Arabia, but I never had a situation where the sand was hitting the lens at high velocity. Generally, a lens hood provides good protection because even wind directly aimed at the front element piles up and creates a dead space immediately in front of the lens. More often, the issue is ricocheting low-velocity sand accumulating around the filter threads etc which requires care (blower bulb, long bristle brush) to remove so it doesn't get transferred to a cleaning cloth and then inadvertently used to scour the lens. A the sea shore, I think the issue is often that salt spray becomes gummy and traps sand and silica dust as it hardens, so it must be removed carefully with a wet method.

--AP
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Old Tuesday 15th October 2019, 17:17   #40
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I have a note, relating to my 1978 Leitz Trinovid 10x22C, that says ""plain glass cover plates over objectives".

Not sure if that's true, however. Have other manufacturers done this, in the past?

I don't think they are field-changeable, so perhaps it's just a cost-saving measure by the manufacturer, i.e. it's cheaper to replace the plain cover glass, than part of the objective?

Or perhaps it wasn't true, and I noted it down in error.
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Old Tuesday 15th October 2019, 18:14   #41
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Originally Posted by cdmackay View Post
I have a note, relating to my 1978 Leitz Trinovid 10x22C, that says ""plain glass cover plates over objectives".

Not sure if that's true, however. Have other manufacturers done this, in the past?

I don't think they are field-changeable, so perhaps it's just a cost-saving measure by the manufacturer, i.e. it's cheaper to replace the plain cover glass, than part of the objective?

Or perhaps it wasn't true, and I noted it down in error.
The Nikon 8x40 Classic Eagle focuses by moving the objectives and so is made waterproof by a sealed glass window in front of the objectives. I think the Swarovski 8x30 SLC is the same. There are other old bins like that. The original version of the Swift 8.5x44 Audubon roof-prism (before the 828HHS) had a window over each moving ocular lens to seal them, so eye-relief varied according to how focus was set! All of the above are models from yesteryear but I know of at least one current bin that has a flat glass in front of the objectives--the Pentax Papilio.

--AP
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Old Tuesday 15th October 2019, 18:17   #42
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ah, of course! thanks very much Alexis, most interesting.
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Old Tuesday 15th October 2019, 18:20   #43
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Quote:
Originally Posted by Alexis Powell View Post
The Nikon 8x40 Classic Eagle focuses by moving the objectives and so is made waterproof by a sealed glass window in front of the objectives. I think the Swarovski 8x30 SLC is the same. There are other old bins like that. The original version of the Swift 8.5x44 Audubon roof-prism (before the 828HHS) had a window over each moving ocular lens to seal them, so eye-relief varied according to how focus was set! All of the above are models from yesteryear but I know of at least one current bin that has a flat glass in front of the objectives--the Pentax Papilio.

--AP
The little Leupold Rogue 8x25 bins in my office desk at work are the same way... Flat glass over both objectives.
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Old Tuesday 15th October 2019, 21:34   #44
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The Canon 18x50 IS and 8x25 IS have optical windows as do some of the others but not all.
The Minolta Mariners? also have front windows.

The 4 inch f/1.8 lenses were moving at 500 knots 250ft above the ground, terrain following.
Quite a ride.
Maybe some were angled forward. Usually there would be 3 cameras operating.
With image motion compensation.

The Wild 98mm f/1.4 lenses are marked with the focal length measured for each lens to 0.01mm at 80 metres.
I suppose these also had filters, so I don't know how the image scale was affected or the focus.

B.
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Old Wednesday 16th October 2019, 12:54   #45
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I have a note, relating to my 1978 Leitz Trinovid 10x22C, that says ""plain glass cover plates over objectives".
Not sure if that's true, however.
Yes, the Leitz 10x22 (and the 8x20 of the same style) had plain glass over the objectives.

Gary.
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Old Wednesday 16th October 2019, 15:35   #46
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Yes, the Leitz 10x22 (and the 8x20 of the same style) had plain glass over the objectives.

Gary.
It should be noted that most of these are called cover glass, fully multicoated
with AR coatings.

Jerry
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Old Wednesday 16th October 2019, 19:12   #47
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We are using B+W filter in our astronomical setups - they are slightly bigger (for Zeiss 135/2), but I think the conclusions carry over - we have measured transmission in the lab, in most of visible spectrum it's above 99% and we do not see any disturbance in image quality at all. This obviously doesn't test reflections (we use it when it's pitch dark) nor condensation issues (we use heating) but from purely optical throughput, the filters should be impossible to notice by eye at binoculars magnification.
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Old Wednesday 16th October 2019, 19:57   #48
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The cover glass or optical window on the Minolta Mariner 8x32 here is uncoated.
The binocular is a mixture of single coats, multicoats and uncoated prisms.
The binocular is dim, but reputedly tough.

a c.2001 Canon 18x50 IS has purple coatings on the optical windows. Probably single coated or possibly double coated?

There is a new intercom panel about 25 metres away that I can't read with normal binoculars.
I tried a hand held 20x50 old Kowa spotting scope and couldn't read the small writing.
I thought I needed to set up a large spotter on a tripod
But the Canon 18x50 IS showed all the writing bar one word when I switched the IS on.

I then took 5 hand held photos with the pocket size Canon SX730.
All revealed the full text at 40x optical and 4x digital zoom.
With my eyes I would need a tripod mounted good 25x or 27x spotter to see the same detail.
This is really impressive for such a small camera.

But the Canon 18x50 IS did better than I thought.

B.
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Old Wednesday 16th October 2019, 21:29   #49
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Yes, the Leitz 10x22 (and the 8x20 of the same style) had plain glass over the objectives.
thanks Gary; do you recall the main reason for this?

Some have suggested to allow waterproofing, so that there's a fixed external element that's easy to seal, rather than a focussing objective.

But it occurs to me that the 1970s compacts, in particular, probably weren't waterproof/gas-purged anyway? At least, I don't have a note of mine being so.

Or just better sealing in general, e.g. to keep dust out?
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Old Thursday 17th October 2019, 00:56   #50
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a c.2001 Canon 18x50 IS has purple coatings on the optical windows. Probably single coated or possibly double coated?

B.
Canon uses optical windows on their 10x42 as well, perhaps to help protect the expensive objective elements which are very little recessed. It is a helpful indicator that sealing has been lost when these windows fog up.
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