On the subject of the aiming point of a lnb (particularly that of a 120cm Channel Master) I have read all the posts re parabola programs for calculations and carried out calculations and measurements myself. I have read a multitude of articles, in great depth, and I concur with Rima's view that the aiming point does
appear that it should be slightly lower than it actually is if you assemble your dish as it was designed originally', i.e. as standard!
But, I still have this doubt that there is some aspect of wave pattern acceptance/design/signal compromise etc that us hobbyists just don't have enough knowledge of, which is why it has been designed as it is. Here is an extract from "Microwave Antenna Book"
www.qsl.net/n1bwt/app-6b.pdf
Now I can't find a reason for the feed to be aimed at the centre (I have only read about half of the book), but there obviously is a reason!
Now it will probably turn out that we can squeeze some more out of a CM dish by adjusting the aiming point and locating the phase centre of the lnb at the focal point of the dish, but even that may not prove that the dish was poorly designed, it may be an aspect of dish design that all manufacturers take in to account that we are not yet aware of!
We have to consider that these dishes have to work with a multitude of lnbs, potentially with different aperture angles and different f/D ratios so the final design might possibly be a "standard" industry compromise or an aspect of dish design that allows manufactures to cover these variables, a sort of "jack of all trades" approach?
Another thought is that the dish was designed 20 odd years ago, maybe technology has advanced and modern universal lnbs present different problems to frequency range specific lnbfs that were commonly used back then. Yes, I am aware that the "physics" will still be the same.
It might be worthwhile, if Rima can?, to include a matched Channel Master feed horn and lnb, possibly a modified IBU, in the comparison (yes, it becomes
more complicated!)
It's all just food for thought!;)