Agree...I owned one for a while. Nice glass, solid tracking. Finicky parallax was its weakness on mine.
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I really wish people would stop misnaming things. You are talking about the side focus here, it's not an adjustable parallax. So what model March did you own?
The March 2.5-25X42 is a great little scope with amazing capabilities that sometimes are not fully appreciated by some users.
The scope is short and has a humongous zoom range and that will create issues for depth of field ranges for people who do not apply some concepts in their usage of this magnificent scope. As you no doubt know, the magnification of a riflescope is calculated by dividing the focal length of the objective lens group by the focal length of the eyepiece and then adding in the zoon range of the erector assembly. The image formed at the FFP is a function of the objective lens group so the depth of field of that FFP image will be determined by the focal length of that group and its f-number. For this riflescope, I guesstinate the focal length to be 100mm and with the 42mm objective, the F-number will be about f/2.4, a rather fast lens. With the 52mm objective, the F-number is about 1.9, which is really fast. The issue with an f/2.4 is that the DOF is rather shallow at base magnification. Now, for hunting, I would think that a magnification of about 5-7X is plenty sufficient, unless one goes after varmints, This means that the zoom value would be 2-3X for hunting situations. That would make the usable DOF pretty deep and the side focus would not be so touchy,
However, I realize people like to pour on the magnification when it's available and when you go past 4 or 5X on the zoon, I should think the Circle of Confusion value that was fine for lower zoom setting will start to impact the IQ at higher zoom ranges. So yes, when you start using 8-10X or beyond with this wonderful short scope, you will want to get the side focus set much finer than when you're going from 2.5-7 or 8X.
This scope is excellent for hunting at lower mags without the focus being too critical, but it also has the capability to go all the way to 25X and there you absolutely need a very precise side focus setting, because the DOF is very shallow when using the appropriate CoC value for the 8-10X zoon ratio. I hope this makes some sense to you. To recap, at lower mags, the side focus is not critical but as you increase the power, the side focus becomes very critical. One way to do this is to set the side focus at the highest magnification and then lower the zoom to what you need. Do not do it the other way; setting the side focus at 2.5X and then zooming up to 25X.
