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Is 16X REALLY the max usable magnification?

 
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  #8  
Old 02-11-2005, 06:41 PM
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Location: California
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Re: Is 16X REALLY the max usable magnification?

Dixie: The answer really depends on the weather and shooting conditions. In early spring and late fall when the weather is mild (at least here in the west) I can use magnification up to about 22-24x. If the whether gets hotter, or my barrel gets hotter, then mirage becomes a factor and the maximum magnification I can use is about 12-14x, sometimes less on those 100 degree summer days. I have been using the Leupold 4.5-14 on most of my rifles and have been pleased. I do keep have a 24x and 6.5-20x on a couple of long range rifles. I have a 3.5-10 Mark 4 on my 243 AI. There are times when I could use more, but after a couple of shots down the pipe, barrel heat becomes such a factor that anything above 10x is not usable.

Something else to consider. I have noticed on the Leupold variables (that is all I shoot) that no matter what the conditions, clarity seems to suffer at the highest magnification settings. For example, I generally don't go above 12x on my 4.5-14 and above 18x on my 6.5-20. The last two setting are just not as clear to my eyes.

Bob
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  #9  
Old 02-11-2005, 08:29 PM
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Location: Palmer, Alaska
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Re: Is 16X REALLY the max usable magnification?

I for the most part use the 5.5-22x56 NF NXS and it stays on 22x for 95% of my shooting... half-ass mirage or intense mirage either one. Only in the worst situations where the target shape is literal falling apart do I benifit from powering down some.

Mirage gives definition to the invisible mass of moving air between you and the target. The very best indicator of these air mass's intensities and vectors is mirage.

A side focus scope offers a great advantage in that quickly focusing on mirage at a few intermediate ranges before your target as one would wind flags helps with a more accurate assessment of the full value wind component.

I'd get up to a 22x to a 24x top end variable power scope, no way I'll top out at 16x if I spend the money on a scope for LR.
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  #10  
Old 02-11-2005, 09:35 PM
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Just say MO - Is 16X REALLY the max usable magnification?

[ QUOTE ]
5.5-22x56 NF NXS

[/ QUOTE ] considered by the 1000 yard shooters at BH to be the best scope.
I actually crank my Nightforce 12-42x56 up to 42 on occassion. I want a 5.5-22x56 NF NXS but you can get a slightly used Leupold Vari-X III 8.5 - 25 x 50mm Long Range Scope for $500 on eBay (if you'r patient). They have plenty of Leupold 6.5-20x50 even cheaper - I wouldn't go smaller than that for ultra long range shooting. I'm sold on paying extra for the 50mm but plenty of folks find the 40mm works fine.
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  #11  
Old 02-13-2005, 02:06 AM
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Re: Is 16X REALLY the max usable magnification?

3sixbits, I consulted a friend who has a PhD in Physics and Astrophysics as I disagreed with some of your conclusions. Below is his thoughts:
Greetings, I have a Ph.D. in physics so let’s walk through these concepts and see if we can un-confuse ourselves.

According to Webster’s Dictionary, “mirage” is any “optical phenomenon, especially in the desert or at sea, by which the image of an object appears displaced above, below, or to one side of its true position as a result of spatial variations of the index of refraction of air.” However, because we are discussing long-range hunting, we can limit our interest to the effects in the atmosphere which occur within approximately 8 feet of the planet’s surface.

During the day, light from the Sun warms the surface of the Earth. The air near the ground can then absorb some of this heat. Since hot air rises, this newly warmed air moves upward. Light reflecting off the target you are trying to hit passes through this rising air and is slightly deflected. This displacement of light due to heated, rising air is what hunters usually refer to as mirage.

Mirage can occur on hot or cold days. All that is required is for the Sun to warm the ground above the temperature of the air.

Following are my comments addressing the previous posting of others:


Comments from one person:

>> “From a physics standpoint, you must have a heat source present to warm the air. Warm air rises or moves in relationship to its cooler surrounding air, and it is the rising air that we call mirage. Regardless of the outside temperature, a heat source (like the sun) is necessary. Mirage can be worse in cold temperatures since the sun can cause a slight temperature difference easier in cold weather which
causes the slightly warmer air to rise.”

These statements are correct. The only addition I would make would be to point out that, while the Sun is the ultimate source of the heat, the air is being warmed by the heated ground.


Comments from a second person:

>> OK Your kidding right? You didn't know that the planet we live on has an internal heat source?

The Earth does have an internal heat source in the form of a molten core. However, this has almost nothing to do with atmospheric phenomenon. The heat from the center of the Earth is released through geological phenomenon like volcanoes, geysers, and sea-floor spreading zones. It has a large affect on the inside of the Earth, BUT at the surface of the Earth, the Sun provides 20,000 times more energy than geothermal energy of the Earth. The Sun is the primary source of energy for both the atmosphere and the oceans.


>> You did know that outside the earth atmosphere that space is at absolute zero?

The fact that the space is colder than the surface of the Earth is correct. However, weather phenomenon happen in the troposphere (the bottom 10 kilometers of the atmosphere). You don’t reach space until you climb to an altitude of over 400 kilometers.

Additionally, deep space is actually at 2.7 degrees above absolute zero. Because the Earth is fairly close to the Sun, the space above Earth is not even quite as cold as deep space.

Absolute zero is the temperature at which ALL motion stops – even the motion of electrons moving within atoms.


>> You must know that the law of thermal dynamics still apply when the sun is shining on the other side of the planet and you are in beddy-by? Heat still travels to cold!

Actually, our atmosphere is very complex due to the motions of warm and cold fronts, the jet stream, the effects of varying land and water masses, etc. The fact that the Sun is heating the other side of the Earth during the night has very little effect on the weather experienced by the people on the night side; it takes considerable time for heat to travel 12,500 miles (1/2-way around the globe).

In addition, heat is only guaranteed to travel towards cold when you are discussing the concept of conduction (heat transfer due to physical contact – this is what occurs when you place your hand on a hot surface). Conduction is of little consequence when discussing large-scale atmospheric movement. Heat in the air is moved primarily by the motion of large masses of air (convection). If this were not the case, a cold front could never move over a location that was experiencing weather due to a pleasant warm front.



I hope all of that helps. Have a good evening!
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  #12  
Old 02-13-2005, 06:56 AM
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Join Date: Jan 2005
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Re: Is 16X REALLY the max usable magnification?

I'am afraid your friend doesn't know much about thermal dynamics. Heat transfer in other ways than by contact. You do know the tempture goes up the deeper from the surface we dig . Thats why deep mines have to use ac in the old days they used ice.. Heat still travels to cold. Wheather or not objects come into contact with one another . The night sky effect is a prime example. Is an overcast night warmer than a clear night? Overcast you have in place insulation between the sky and the earth. Thats why it takes longer for the earth to loose it's temp when its overcast. Ask your astrophysics buddy why the stars appear to twinkle? This isn't heat waves?
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  #13  
Old 02-13-2005, 10:32 PM
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Re: Is 16X REALLY the max usable magnification?

My 20 power scopes are always on 20 power and my 32 power scope rarely gets turned down below 24 power. 16 power is just not enough for long range varmints.
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  #14  
Old 02-21-2005, 02:38 PM
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Join Date: May 2001
Posts: 18
Re: Is 16X REALLY the max usable magnification?

I spoke with a gentleman who extensivley shoots and tests long range ammo and rifles at the Boulder City range outside of Las Vegas, Nevada. They often shoot early in the evening through late night hours (lit targets and no neighbors to bitch about noise) so they crank the Nightforce NXS scopes to highest magnification. No heat, no mirage. In the heat of the day they crank back down to usable magnification. He recommended the 5-5-22X for military application, and 8-32X for NRA-style long range competition. He recommended a 12-42X for shooting if you don't plan on targets closer than 600 yards away (since it has the smallest elevation adjustment range).
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