Accurate range-finding through Heat Haze?

Discussion in 'Hunter (HFT) & Field Target (FT)' started by JerryD, Jul 18, 2010.

  1. JerryD

    JerryD Member

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    I was setting up a scope yesterday and trying to calibrate the sidewheel. Once out past 45yds I was having to deal with heat shimmer, which made it near-on impossible to discern a clear focus point. In the event I waited for a downpour and the sky to cloud over. The settings I got without the shimmer were different to the earlier settings, right down to 30yds.

    That's OK when dealing with known distances but on a course the whole point is you don't know how far they are - that's why we parallax! I'm think of resorting to bracketing when the heat shimmer gets too bad, but that involves holding the image steady enough to bracket accurately. Telling the difference in size between 50 and 55 is not easy - not for a wobbly bugger like me, anyway:rolleyes:

    How then do you deal with heat shimmer when trying to rangefind when it's hot:confused:
     
  2. Willbe

    Willbe I Like BIG Hats!

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    You struggle!!! ;)

    Seriously though, not sure if it's the right thing to do but I tend to still try to make a comparative judgement to where is the best (if still poor) picture and go from there.
     
  3. RobF

    RobF Administrator Staff Member

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    Struggle... but i tend to take quite a few stabs and then go in the middle.. and if i can i try and get it mid shimmer..
     
  4. Conor

    Conor Never been banned from sales Staff Member

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  5. JerryD

    JerryD Member

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    What, even with the March?:p

    The perceived change was about 5yds between shimmer and non-shimmer. Since the air temperature stayed pretty much the same (or at least felt that way) it beggars if heat shimmer is responsible for frequent mis-ranging. Did youtr experiments cover heat shimmer, Rob?
     
  6. RobF

    RobF Administrator Staff Member

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    :D

    a better scope can't solve heat haze... the wandering mirage shimmer effect you see is layers of air at quite different temperatures, very close together, in direct sunlight... a better scope can handle the bright blur off bright objects, but it's never going to solve that shimmer. You still see a shift in range as the air focuses the light rays closer and further away because as air heats up and cools it changes the index of refraction (or the amount it bends light).

    If you wait until the wind blows, it gets better... the worst type isn't the small shimmer you can see move, it's the big shimmers that you can barely see move, that as you say, put a target 5 yds in and out.

    The only thing i've found is to work with is to keep ranging and get the closest and furthest ranges, and go down the middle of those.
     
  7. Mr P

    Mr P Active Member

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    Hi Jerry what scope are you using? I personally have used leupolds and they behave quite well, but you do have to work with them but as i tell everyone they are not for everyone i do beleive rob struggled with his
    i suggest you set your scope on a day around 15-20* centegrade and overcast using a proper field target
    and only focus on the threaded ends of the string or the swivel it will take you time and it may take you several times untill you are really happy with the results
    steve
     
  8. Jon

    Jon Member

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    It will be a Bushnell 6500 Steve.
    Theres a few that do alright with them.

    Personally i would say dont concentrate on the heat haze look at what you want to see and use in normal manner.
     
  9. luddite

    luddite I Love HFT

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    Try a Burris R/A 8-32x44, cuts through heat haze, no white out ever. :D
     
  10. JerryD

    JerryD Member

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    ...... wonder how he got that one right??:D Sidewheel works a treat, Jon. Set-up's 2lbs lighter now I've switched. Had to use a lotta weight just to balance the NXS. The Elite's lighter and more compact, and doesn't shift the point of balance forward too much.

    Having moved up in glass quality I've found that the better the glass, the more you see the heat haze - which is why I'm asking. As Rob says, it's nothing to do with the scope. I know it's caused by the change in the refractive index of the air with temperature, so UV or polarising filters etc. can't really help. I'm just trying to find if there's a better way than "struggling with it".


    .
     
  11. RobF

    RobF Administrator Staff Member

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    the only way i've found is to give it as many stabs as time will allow, and ideally try and keep my concentration on one fine aspect, and when that's clear hope it comes in the middle between shortest and longest ranges... i think struggle with it is the term of the day for me still :D
     
  12. RobF

    RobF Administrator Staff Member

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    that and asking course designers not to put their dark black targets down low on cool grass on hot days :D :D
     
  13. JerryD

    JerryD Member

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    ........ don't be giving 'em ideas now, Rob!! :D:D:D


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  14. holly

    holly Well-Known Member

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    If .

    if the target is on a tree . go up the tree above the heat haze , then knock a yard off . the best scope i have used for seeing through heat haze is the 35 mag conp X . the scope does not need a defined target to rangefind . just get it as clear as you can and use that , seems to work . or at least it did at bisley where in the summer there is a lot of heat haze in the open bits ??? HOLLY
     

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