But powerful and expensive microscope doesn’t fix it either. AM software fixes it.
Possibly 'mtemur' !
However the good news for us vinyl audiophiles is that Wally Tools do use an expensive and powerful (magnification) microscope set-up to be able to determine the 'zenith error' accurately for cartridges and then make and provide a shim to fit between the top of the cartridge and bottom of the head shell to compensate for this 'zenith error'.
Wally Tools undertake this service in-house as part of setting up one's cartridge for all the parameters. And if you are a Kuzma 4Point owner if you also send them a spare Kuzma 4Point head shell with your cartridge, they will send you back your cartridge fitted to the head shell with a custom made shim specifically for your cartridge and Kuzma head shell so the cartridge can perform to it's optimum performance (as long as you set up your 4Point tonearm correctly i.e. with the 'Wally Reference' and 'Wally Skater' tools for instance).
I believe (from their information) Wally Tools have looked at many many cartridges for customers who have sent their cartridges in for assessment and setting up and now have an excellent database of information of cartridges they have set-up (and therefore know of their imperfections in particular 'zenith errors' amongst all of the other parameters). From this information, I also believe that there is a repeatable pattern amongst cartridge manufacturers of cartridges that have been built by the cartridge manufacturer so badly that the cartridge has had to go back to the manufacturer to be corrected or even completely replaced with a new one (
and this includes very expensive so called 'top of the premium league' cartridges too !)
So from me learning about all that Wally Tools can do and have learnt about cartridges etc., in the future when I buy a new and expensive cartridge I will get the Dealer or Manufacturer I have bought it from, and have them send my purchased brand new cartridge direct to Wally Tools for analysis and set-up and I will send Wally Tools one of my spare 4Point 11" head shells.
The only reason why I haven't used this service from Wally Tools (although I did seriously consider it before I calculated the overall financial cost to me (as I am based in the UK at the moment)) is that my current MSL Eminent Ex cartridge had already operated for 600+ hours after approx. 11 months of play time (therefore I knew that I would be changing it for a new cartridge in July / August 2024) and the overall cost (i.e. Wally Tools analysis and set-up cost, very expensive postage (because of the high insurance costs and an express delivery from UK to USA and back) and buying a brass custom made shim) came to over £1,000 !. So instead, I used this money to buy the Wally Scope and attempt to set-up my cartridge myself (currently minus the 'zenith error' assessment - as I mentioned in one of my recent previous posts on this thread).