Rifle Scopes mirage? help me undertand it

[hershey]

the more i surf here, the more i learn.

in a recent post i was asking questions and the answer i got back mentioned mirage and made reference to scope quality. i do not fully understand mirage, but know that different things make it worse, mostly sunshine, and ground temp plays a role too. but how does scope quality play a role in this, is it coating, tints, or design or ?

 

[LoneWolfUSMC]

Re: mirage? help me undertand it

I can tell you that I have seen mirage in every scope I have looked through and higher magnification makes it more apparent. Adjustable objectives allow you to focus on the mirage to better read it without a spotting scope.

Mirage is a fact of life. Until we figure out how to make a scope to change the laws of physics I don't think you are going to be able to "reduce" mirage. The more precise the view through the scope the more the distortion caused by the atmosphere will be apparent.

 

[73MCRD]

Re: mirage? help me undertand it

Go to a good 4 or 5 day long range class and you will walk away knowing everything about mirage.

 

[cducati]

Re: mirage? help me undertand it

learning to read it is very helpful. Good glass will help you see it better.

 

[Dogtown]

Re: mirage? help me undertand it

Yup, we live in a fluid environment - the air - and that fluid is constantly flowing. The ground absorbs heat from the Sun which is radiated back and warms the air. This causes subtle perturbations in the air (remember, it's a fluid), creating pockets of variable density which in turn creates subtle variations in heat. Air hardly refracts light (IOR of 1.0) compared to say water (IOR of 1.3) or quartz (IOR of about 2.2). But the temperature variations in the air cause subtle refractions which in turn displace what we see - ie creating a mirage effect.

Where "reading the mirage" comes in is that even the softest wind affects the mirage pattern, giving you velocity (speed & direction). So by watching the mirage you can often judge subtle wind velocity. Now looking through a scope gives you a Field of View (FOV) and higher magnifications gives you much tighter FOVs (think wide angle camera lenses vs telephoto). Mirage can be a problem for higher magnifications because in a sense more air is "compressed" into the viewing plane and the displacement of the view is amplified. Hmm, I don't know how else to explain that part. But higher quality scopes will give you better optical clarity and adjustable parallax to deal with the mirage.

In the next 30 years I think the high end scopes will be digital devices with adaptive image processing that will be able to mitigate or enhance environmental distortion effects.

 

[Bunkerdog]

Re: mirage? help me undertand it

thank you dogtown---your explanation was very easy for me to understand---my background is photographic---learning to "read the mirage" must be like depth of field in a long focal length lens---as hershey says, i learn more every day on this forum