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Mirage Reduction

Oh cripes, now Dan is going to give me grief for revealing how it works.

I ran some numbers for grins.

Here are 3 standard objective sizes that you find on LR scopes. I calculated the diameter needed to reduce by 1 EV, 2 EV and 3 EV: Sizes are all in millimeter:

Obj at 60: 42, 30, 21
Obj at 56: 40, 28, 20
Obj at 52: 37, 26, 18

I'm thinking that any more than 3 EV it will be too dark. I'm even thinking that 2EVs is a lot, except probably on very bright days. I'm also not sure if half-EVs are needed.
 
A friend found out that additionally, they showed the mirage over that increased depth of field, which he could never decide was advantageous or disadvantageous.

I've never bothered. Where I shoot in Australia, there will be mirage & the mirage will give you information on wind movement, so why try to hide it? Filtering it out, or lowering magnification so your brain is comfortable with the sight picture doesn't change what's happening - just gives you a feeling of comfort.

John the mirage is bad enough here that at times the target looks like a boiling blob, making it very difficult to discern an accurate point of aim. When the x count separates the winner, I need all the help I can get.
 
So what about a single objective reducer, but mount it 75mm away on the sunshade extension? Does this have the same effect as one with a smaller hole? .....Carl



Oh cripes, now Dan is going to give me grief for revealing how it works.

I ran some numbers for grins.

Here are 3 standard objective sizes that you find on LR scopes. I calculated the diameter needed to reduce by 1 EV, 2 EV and 3 EV: Sizes are all in millimeter:

Obj at 60: 42, 30, 21
Obj at 56: 40, 28, 20
Obj at 52: 37, 26, 18

I'm thinking that any more than 3 EV it will be too dark. I'm even thinking that 2EVs is a lot, except probably on very bright days. I'm also not sure if half-EVs are needed.
 
Ray for me in Fclass their is adequate time so I would quickly experiment with and without the aperature to find out which is better. That is if I was not able to evaluate in advance.
 
So what about a single objective reducer, but mount it 75mm away on the sunshade extension? Does this have the same effect as one with a smaller hole? .....Carl
It's all based on the field of view of the scope at various magnification. If your sunshade is not causing any vigneting of the image, the distance to the aperture device is incidental; it will work the same way 75mm from the objective or right at the objective. I would have to do some math to come up with a length at which it will this will change.
 
If the diameter and thread is the same, yes. You might ask Shiraz about the thread pitch. I believe it is metric, (0.75) and the NF is Imperial.

Edit: You could have a step-down ring made, but it would be expensive.

Own a front Butler Creek flip-up? Might try experimenting with Pin Holes... Not telling you to drill your BC while on your optic.... Smaller the hole, (aperture) better the depth of field gain. 35mm is about 1.45". Might try a .75" holesaw and work your way up, if you have a holesaw set.

Try a good camera store. Some filter holders use a clamp-on assy to attach to lenses. Tiffen makes a square holder for gel filters. Could use heavy cardboard with different hole sizes or aluminum etc and have different apertures for whatever conditions.... Too bad Merit don't make an adjustable aperture for objective use. Might be able to find a used view camera aperture that is not integral with lens and adapt that for scope objective... There's also taping construction paper over your sushade and trying holes of varying diameter
 
Most all March scope comes with a 35MM Modifier Disk. I've used one in competition since the 2013 season. They do work because they may cut the incoming light by as much as 50% and your depth of focus increases by as much as 50% also.
Just to be clear: you are saying that a scope can cut through the mirage, thereby seeing more of the erect image/target? What is the mechanism which accomplishes this? Are there demonstrations of this? I'd like to see them. Thanks.
 
The item provided with the March scopes is called a Modifier Disk. It is a thin disk with a 35 mm hole and is equipt with a threaded mounting ring that fits the objective end of the scope. When in place, it will:

Reduce light through the scope 50-55%. -- This may be usefull under bright conditions.

Increase depth of focus about 50%.

Reduce resolution by 33%. -- In bad seeing conditions (including particulate air pollution and mirage particularly with changing wind conditions), the normal high resolution of the scope may show too much detail for the user to interpret usefully. Reducing the resolution reduces the visibility of detail without having to reduce scope power.

Note: In simple terms for our purposes I define resolution as the ability to determine if two bullet holes in a target at a particular distance and of a particular size that overlap by 50% are in fact two holes and not just one. If you reduce the objective aperture size you will have to either move the target closer or increase the bullet diameter to be able to make that determination.

Using the Modifier Disk can be very helpful in those afternoon relays when the mirage and wind would otherwise make target sighting and analysis very difficult.

The Modifier Disk works by reducing the clear objective diameter (aperture) which in turn reduces the visibility of small details (reduces resolution).

Before the enthusiasm for using the March Modifier Disk or any other aperture reduction gets out of hand please remember that with the potential benefits there are also some performance sacrifices. The following opinion on use of the Modifier Disk is based on my experience over the last 10 seasons. At or over 300 yards I only use the Modifier Disk under extreme mirage conditions do to the loss of resolution needed for aiming and analysis. For 100 or 200 yards there is sufficient resolution with the Modifier Disk on for use in moderate or worse mirage. However, I have also found that the more I use the scopes without the Modifier Disk and thus train my visual system to deal with the more data rich images, the less I feel the need to use them and the better I am able to aim precisely and analyze my bullet hole patterns.
 
I have been shooting March with ED (and now Super-ED) glass for close to 8 years now and that has helped me deal with the IQ degradation due to mirage. In the last two outings, I have tried the MD on my March-X 10-60X56 and I have found that I see more mirage due to the greater DOF but since I have been using these scopes for so many year, looking at the same target, I did not find that the target was defined any better. I have stated numerous times that I have been shooting at 40X regardless of mirage for years, and that I have increased to 50X with my 10-60X56 due to its Super ED glass.

I agree with Fred about training the visual system to shoot through the mirage. I use the same scope, at the same power, in all conditions and mirage is never an issue with respect to aiming even at 50X.
 

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