Shimmering effect on Scope - effected by Cold?

[Peter Hodgkinson]

I have a 6.5x 20x 50mm Whitetail Classic, imported from USA. [At the time I was told by a Guy in Simmonds technical that they were really Whitetail Expeditions and optically excellent value for money but had the wrong finish for that range [due to an ordering cock-up]and hence were sold off within the cheaper Classic range.

Anyway shooting from a very warm dinning room last week into a coldish garden seemed to give a wierd effect, a sort of shimmering as the target went in and out of focus. A bit like the effect of heat-haze on sand ot tarmac.
I put the gun on our custom-made gun bench [20mmx20mm solid stainless steel] so it was totally rigid and I still got the same effect.

I waited till the wife came home and asked her opinion. She said it was a bit hazy, and also saw the same effect so I looked again and was suprised to find that it was now fading in and out of focus much less than before. By now with the door open the room was a bit cooler.
Is this normal? or are there gases in the scope, and if so have they leaked to produce this effect?
Any views on this much appreciated as i obviously can't ask the US supplier for there opinion.

[hareng]

More than likely picking up a heat haze that inferior glass does not or may not.
These often appear to move or shimmer but never noticed at close range.

[corkscrew]

dont worry about the scope its fine.
it was just picking up the haze caused by the difference in temp from room to outdoors.

[albrown]

The change in refracive index in going from air to a glass prism causes the light to bend. Same with looking at a fish in water it appears to be in a different position than it really is. The refractive index of a gas ie air, depends on temperature so there is a change in refractive index in going from wamr to cold air. Thus light will bend. The shimmering is due to convection currents of the air....I think

[Peter Hodgkinson]

Thanks guys for your reassuring help.