Having ED glass helps but not enough to say I can leave my magnification up high because it’s high end glass. I’m sure the ca can make it worse that makes sense. I still have to turn down my pmii which has glass that is near what scope companies call super ED.
I have been shooting at the same range with the same target face, year-round for about 16 years now. I have gone through a series of riflescopes. I realize this is F-class, but the precision needed for these targets require magnification and lots of it.
As I said from the onset, ED and Super ED glass does not eliminate or remedy the mirage; this type of glass in not as affected by the mirage as other glass. I have not tested every scope on the planet, but let me tell you what I have observed.
The first riflescope I used for this was a Nikon Monarch-X 2.5-10X44. I was not affected much at all by the mirage, but I could not get the precision needed, especially when the FC target faces were sanctioned by the NRA. I was transitioning from Service Rifle to F-TR and I happened to have that scope handy. It's a great scope, but not for this discipline. I swapped it for a Nikon Monarch 6.5-20X44 and that was better for magnification, and the mirage was not much of an issue. For a little while I used a Weaver T-36 36X40 scope. That got me the magnification I was hoping for and the tracking was great. But the glass was pretty bad and the mirage affected it horribly; to the point I couldn't even see the rings and the aiming black was like a crazed amoeba. I moved on to an Nightforce NXS 12-42X56. An excellent scope with I ran at 40X, but had to drop down to 30X or less when the mirage showed up, which it did all the time in South Texas.
Six years ago, I bought a March-X 5-50X56 and after a few matches, I noticed that I did not have to back down from the 40X at which I was running all the time. I sometimes pushed to 50X, but it was better at 40X in very heavy mirage. I shot with that riflescope, stuck at 40X, year round and all over North America for 6 years. About 100 local matches, a dozen 3-day state matches, a few regionals, a half dozen Nationals (at various places) and one World. Always at 40X, everywhere I went, all the time. There was never any need to back down.
At the start of the year, I acquired a March-X 10-60X56 HM, with Super ED lens. I ran it for a couple of months at 40X, then in the last few months, I cranked it up to 50X and it stays there. The mirage hasn't gone away, and I see it in the riflescope but the rings as highly visible and the target face is not a crazed amoeba, it's the regular face with some shimmering. This past Sunday, I caught myself getting fixated on the image because it was so nice. I could see details I had not ever observed before and I was like a kid in a candy store. March-X 10-60X56 HM: 50X, 1000 yards, elevation 100feet ASL, dead of summer in South Texas.
The top euro scopes probably use Schott fk58 which has a 91 abbe rating & super ED usually means around 95 abbe like fluorite crystal, fpl53, or fcd100 glass then standard entry level Ed usually means fpl51 or something close with an abbe 82-87. In the the telescope world they list exactly what glass is in your scope so I have seen the difference between ED & super ED & the difference isn’t as big as one would think in well designed scopes. At rifle scope mag levels the glass difference would be even less & very difficult to see a difference between glass with 90-95 abbe given equal optical design. It’s even hard to see big differences at telescope mags of 100x or more in quality Ed & super Ed scopes. I asked koshkin about why there are not many scopes are not using fluorite or equivalent glass like super ed. He said it wouldn’t make much difference in rifle scopes as much as telescopes due to mag range & that optical design & coatings would be more important in rifle scopes.
Optical designs and coatings are critical, I totally agree. But I do not believe those have any effect on reducing or controlling the damage done to the IQ by the mirage, whereas I believe ED and Super ED glass does.
Also, Nikon, (which invented ED and Super-ED glass) uses ED, Super ED and even Fluorite crystal glass elements in their camera lenses and the mag ranges are similar to the focal length of the objective part of the riflescopes.
There are several reason why fluorite crystals glass elements are not used in riflescopes: they are expensive, difficult to make, subject to temperature changes, and fragile to boot. I am only aware of one riflescope that had some fluorite crystal element and that was (IIRC) an Hensoldt and the price was north of $7000. It was a 20-some X variable.
March was the first riflescope maker to use ED glass elements and at the moment, they are the only ones using Super ED glass elements. Their ED models have 1 ED element, the High Master Lens System uses 2 Super ED elements, the objective lens doublet.
That makes sense to me now because you can have the same Ed glass in one optic & produce different results in another. Like the mk5hd 56mm handles ca close to my pmii & much better than it’s smaller 44mm counterpart. In higher end scopes the optical quality makes mirage not look as bad I agree. The glass quality will make a difference between low end & high end but how much is hard to say because I turn my high end & cheap scopes to similar powers to deal with mirage. One thing for sure is my high end have a lot better image when shooting longer ranges at lower mag.
March-X 10-60X56 HM: 50X, 1000 yards, elevation 100feet ASL, dead of summer in South Texas.