Spotting scope quality vs air temp

[Alan Griffith]

Yesterday morning, while out getting my feet wetter w/ the '06 Ackley, the temp, of course, was increasing from upper 30's to about 60 when I quit shooting. I have a 25 yr old Bushnell Trophy spotting scope that came with a 16-36 powder adj occular lens as well as the 48x power lens I also bought at the time; I was using the 48x.

As the temps increased, the mirage effect made it to where I could not make out hits on the clean white paper at anything 400+.

My question is if optic quality will help or if even those shooters with big money/power scopes suffer the same due to heat induced mirage.

If optic quality helps, how far out can you see hits on paper and at what temps can you do this to? If it doesn't help, are you just driving down, back and forth, a lot to the target to make heads or tails of what your rifle/load combo is doing?

BTW, at 600 yd I was getting .75 to MOA groups. Probably nothing to some of you but I'm pickled tink!

 

[CatShooter]

The amount of mirage you get is simply a function of the diameter of the objective.

The bigger the scope, the more it is affected by Mirage.

The quality of the optics has no bearing on it.

One solution is to make a cardboard cover for the front of the lens and put a 1/2 sized hole in it so the opening is smaller... this will reduce the mirage.

Leupold used to make a set of threaded plates for their 40mm scopes for that same purpose.

.

 

[uncleB]

[ QUOTE ]
The amount of mirage you get is simply a function of the diameter of the objective.

The bigger the scope, the more it is affected by Mirage.

The quality of the optics has no bearing on it.

One solution is to make a cardboard cover for the front of the lens and put a 1/2 sized hole in it so the opening is smaller... this will reduce the mirage.

Leupold used to make a set of threaded plates for their 40mm scopes for that same purpose.

.

[/ QUOTE ]
Catshooter,
I invite you to re-think this, objective diameter has absolutely nothing to do with mirage, might have more to do with the power setting and other factors.
UB

 

[CatShooter]

[ QUOTE ]
[ QUOTE ]
The amount of mirage you get is simply a function of the diameter of the objective.

The bigger the scope, the more it is affected by Mirage.

The quality of the optics has no bearing on it.

One solution is to make a cardboard cover for the front of the lens and put a 1/2 sized hole in it so the opening is smaller... this will reduce the mirage.

Leupold used to make a set of threaded plates for their 40mm scopes for that same purpose.

.

[/ QUOTE ]
Catshooter,
I invite you to re-think this, objective diameter has absolutely nothing to do with mirage, might have more to do with the power setting and other factors.
UB

[/ QUOTE ]

I don't need to rethink it... I was a director of research in optics at Columbia University for three years.

For any given power, the larger the objective, the more mirage... this is basic bread and butter optics, NOT rocket science.

If you lower the power, you reduce the mirage, but then you can't see the bullet holes.

... and you were saying???

 

[uncleB]

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
The amount of mirage you get is simply a function of the diameter of the objective.

The bigger the scope, the more it is affected by Mirage.

The quality of the optics has no bearing on it.

One solution is to make a cardboard cover for the front of the lens and put a 1/2 sized hole in it so the opening is smaller... this will reduce the mirage.

Leupold used to make a set of threaded plates for their 40mm scopes for that same purpose.

.

[/ QUOTE ]
Catshooter,
I invite you to re-think this, objective diameter has absolutely nothing to do with mirage, might have more to do with the power setting and other factors.
UB

[/ QUOTE ]

I don't need to rethink it... I was a director of research in optics at Columbia University for three years.

For any given power, the larger the objective, the more mirage... this is basic bread and butter optics, NOT rocket science.

If you lower the power, you reduce the mirage, but then you can't see the bullet holes.

... and you were saying???

[/ QUOTE ]
catshooter,
I dont want to get something bad going here, but you should have paid more attention while at Columbia University.
I was at a shoot yesterday and the mirage was EXACTLY the same looking through my 25x 50mm rifle scope as it was looking through my 25x 80mm spotting scope. I had neither bread or butter on either one.
you confirmed what I previously said you said "if you reduce the power,you reduce the mirage" but you then ranted on "but then you can't see the bullet holes".
If the mirage is bad enough you wont see bullet holes through a 10mm objective or a 100mm objective.
"...and you were saying???" re-think this again.
UB

 

[Gene]

I shoot in registered 600 meter groundhog matches. We have tested and compared all brands of spotting scopes. Mirage is the limiting factor, and cutting back on the power setting will reduce but not completely eliminate mirage. Yes, it is then more difficult to see bullet holes. My spotter is a Leica Televid 77mm objective, and it is very good, when conditions are ideal. Other high end spotters are just as good: Swarovski, Pentax and Zeiss to name a few. I discussed this with a gent in Tennessee the other day. He works on all binoculars and spotters. He said, and I agree "The larger the objective, the better you will see bullet holes at 600 Meters if mirage is not a factor".

 

[uncleB]

I must modify my previous post slightly, while the mirage was exactly the same in my rifle scope and spotter the field of view is larger in my spotting scope, so catshooters idea of poking a hole in cardboard will do NOTHING for mirage it will drasticly effect field of view, like putting blinders on a horse.
UB

 

[Jon A]

Uhm, you might want to give that a try UB. You might be surprised.

 

[CatShooter]

[ QUOTE ]
... so catshooters idea of poking a hole in cardboard will do NOTHING for mirage it will drasticly effect field of view, like putting blinders on a horse.
UB

[/ QUOTE ]

Try it before you comment - you couldn't be more wrong if you tried... and so far you are doing a good job.

.

 

[neolithic hunter]

[ QUOTE ]
[ QUOTE ]
... so catshooters idea of poking a hole in cardboard will do NOTHING for mirage it will drasticly effect field of view, like putting blinders on a horse.
UB

[/ QUOTE ]

cat shooter is really wright. my spotter uses a 4" mirror reflex telescope at about 100 power. it has a 6.5" sunshade with a .25" hole in the front of it. it's the only way to see your bullet holes at 400+ reliably on a day when its 100+ degrees out there.

Try it before you comment - you couldn't be more wrong if you tried... and so far you are doing a good job.

.

[/ QUOTE ]

 

[goodgrouper]

Looking through my 80mm obj Swaro spotting scope and then looking through my 50mm obj rifle scope, I couldn't tell any difference in mirage. They both looked like I was trying to shoot through chicken soup! Backing off the power is how I cope but the hole in the cardboard sounds interesting. Might have to give it a go.

Catshooter, do you have a formula or ratio for obj to mirage correlation? Would the diff between an 80 and 50mm objective even be able to be detected by the human eye or is this just an insignificant fact that only exists on paper? I ask because I got out my 32mm rimfire scope this evening and my 80mm spotter and looked up at the mountain behind my house which I have ranged at 1447 yards and I saw no difference in mirage. Both showed thick mirage.

 

[CatShooter]

GG... there is no formula for it.

Next time when you are out on a mirage prone day, take a black paper and some tape.

Cut a nickel sized hole in the middle of it and tape it to the front of the scope so you can lift it up to compare.

Look at a long range target that is in a boil.

Flip down the paper, and what you will see is a sharper target that is dancing.... nothing can make it stop moving, but the smaller opening will make it clearer.

What is actually happening is a long write, and will bore everyone to death... but a classic demonstration of mirage v aperture is the following - take the 80mm scope, and make a paper mask with four nickel sized holes at 12, 3, 6, and 9 o'clock, out by the edge, but still in the light path.

Take the scope out just after sunset and look west at a bright star - you will see 4 starts dancing independently around each other. That should throw some light on the subject. /ubbthreads/images/graemlins/wink.gif /ubbthreads/images/graemlins/wink.gif

.

 

[Freebore]

Catshooter,
So if I drill a hole in the center of my front screw-in lens cover to reduce the visible area of mirage what size hole do you recommend I should drill if I have a 80mm lens (pending availability of a new lens cover). I have an 20-60 x 80mmED Bushnell Elite.

 

[CatShooter]

[ QUOTE ]
Catshooter,
So if I drill a hole in the center of my front screw-in lens cover to reduce the visible area of mirage what size hole do you recommend I should drill if I have a 80mm lens (pending availability of a new lens cover). I have an 20-60 x 80mmED Bushnell Elite.

[/ QUOTE ]

Use a piece of cardboard, it's cheaper.