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8x30 CL diopter shifting with altitude (1 Viewer)

F

fboyd

Member
I have a new pair of Swarovski 8x30 CL binoculars. I'm having a problem where the diopter adjustment shifts with altitude. I live at 400' elevation and both eyes focus correctly with the diopter adjustment set right in the middle when i'm at home. However i also work as a fire lookout at 8800' elevation. When at the tower i have to readjust the right eye diopter way into the negative to be able to focus both eyes correctly. Once i've readjusted the diopter i'm good for the day until i return home and have to reset. What could be causing this? Otherwise i'm very pleased with the binoculars and the views they provide.

I have a pair of Leica Ultravid 10x32 that i also use at home and at elevation and they do not require readjustment between the two locations.

Thanks for any comments or suggestions.

-Florian (New to the forum. Greetings!)
 
It sounds like the reduced air pressure at 8800' is causing the right eyepiece to be pushed slightly outward by the relatively higher gas pressure inside the binocular. Rotating the eyepiece in the negative direction takes the eyepiece elements back in to their 400' position. When you return to 400' altitude the eyepiece has to be rotated back in the positive direction. I don't know why the diopter adjustment would be that squishy, but I've heard of eyepiece bridges on sealed external focus binoculars being pushed outward in response to air pressure changes like that.

The Leicas wouldn't be subject to the effect because their diopter adjustment is entirely internal.
 
It isn't the binocular, it's your eye would be my first thought. It's why when shooting at high elevations my friends have different glasses to shooting low levels.
 
Wilderness Medicine by Paul Auerbach goes into it in detail, cites mountaineering teams and the diopter shift as they climb higher.
 
fboyd said:
But wouldn't both barrels react the same to changes in air pressure?
Click to expand...

No, the left eyepiece is completely immovable. Focus is done by moving internal focusing lenses in both barrels, but the diopter adjustment on the CL's right eyepiece is external, so it could be pushed slightly in or out in response to changes in air pressure.
 
Aircraft cabin pressure is usually set to 8,000ft, so I would expect the same changes viewing from a commercial aircraft.
 
When flying in airliners and using my old Dialyt 10x40BGAs (in which the objective lenses move to focus) the feel of the focus, the stiffness or otherwise of the focus wheel, was different from flight to flight and even within the same flight. I presume this was due to whether the left or right objective was sealing or not, giving variable characteristics to what was, in effect, an air pump as the objectives moved in and out.

Lee
 
The Tridents could descend at 10,000 ft per minute if they wanted.
The engineer had to equalise pressure on the mad descent.
Binoculars would have a hard time.
The cockpit used to flutter at high Mach numbers.
 
I emailed Swarovski tech support and received a quick reply from Michael. This was a new issue for him. He's forwarding my comments to tech support team in Austria. Besides this minor annoyance i'm really enjoying the CL 8x30s.
 
Lee,
The strange thing is that the pilots didn't notice the alarming flutter, whereas it was obvious to me, maybe 1 Hz from memory.
Fuel costs at high speeds didn't figure then.
It took me ages to identify towns in the Thames estuary, when they couldn't understand why I couldn't see them.
Learning anything new takes time.
They had no idea of the power of the Trident engines either in any units.
What was bad about the Trident was that at well below freezing on the ground the fuel became supercooled and it was impossible to de-ice the wings. Even after hours of trying.
I switched flights to a Boeing 727 which didn't have this problem.
On one flight a Caravelle engine broke a fan blade on take off and sounded like a bad washing machine. We landed very fast and beautifully on the remaining engine after a couple of minutes. Captain Makinen, wonderful pilot.
The Caravelle I think shared the front fuselage with the Comet. Very strange.
I asked one pilot if he could roll the Trident if he wanted. He said yes. But I thought maybe not with passengers. It handled like a military aircraft.

I only used my Frank Nipole 7x23 micro binocular. It was so leaky pressure didn't matter.
Camera zoom lenses inhale dust a lot, but primes not so much unless they are Nikon.

I did however, find that I was almost completely deaf after some Trident flights until I swallowed a drink of water. I hadn't noticed it in these rapid descents. My ears just popped. I suppose this effect of pressure could be useful for the henpecked.
 
Binastro said:
Lee,
The strange thing is that the pilots didn't notice the alarming flutter, whereas it was obvious to me, maybe 1 Hz from memory.
Fuel costs at high speeds didn't figure then.
It took me ages to identify towns in the Thames estuary, when they couldn't understand why I couldn't see them.
Learning anything new takes time.
They had no idea of the power of the Trident engines either in any units.
What was bad about the Trident was that at well below freezing on the ground the fuel became supercooled and it was impossible to de-ice the wings. Even after hours of trying.
I switched flights to a Boeing 727 which didn't have this problem.
On one flight a Caravelle engine broke a fan blade on take off and sounded like a bad washing machine. We landed very fast and beautifully on the remaining engine after a couple of minutes. Captain Makinen, wonderful pilot.
The Caravelle I think shared the front fuselage with the Comet. Very strange.
I asked one pilot if he could roll the Trident if he wanted. He said yes. But I thought maybe not with passengers. It handled like a military aircraft.

I only used my Frank Nipole 7x23 micro binocular. It was so leaky pressure didn't matter.
Camera zoom lenses inhale dust a lot, but primes not so much unless they are Nikon.

I did however, find that I was almost completely deaf after some Trident flights until I swallowed a drink of water. I hadn't noticed it in these rapid descents. My ears just popped. I suppose this effect of pressure could be useful for the henpecked.
Click to expand...

David

Didn't Trident (this is the airliner not the intercontinental ballistic missile) have a landing speed like a fighter? I mean it didn't have the low speed lift necessary to 'float' down but had a 'OMG here we go' sort of landing?

Lee
 
Lee,
I think maybe the opposite.
That it was messed around with by the government and British airlines, to land on short runways in Africa and our 'Empire', which meant that the B 727s won all the orders as they used long runways.
But I must check if my memory is correct.
The last ones had 3 and a half engines. I.e. a smaller engine to run everything else besides flying it.
It was a hot rod, but so was the souped up B 727.
It was so underused initially on shared routes, sometimes there were only 3 passengers, with an air hostess each.

P.S.
You are correct Lee. I am wrong.
BEA specified 6,000ft runways and reduced the size of the aircraft making it uncompetive.
The later B 727s etc only needed 4,500ft.
The Trident often cruised at over 610mph, Mach 0.88 or more.
It was so messed around with that the later Boeing got all the orders.
My friend flew B 727s and they are also fast.

That is the problem with many British things. We got there first and others reaped the benefits.
 
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