What is the Best Tool to Measure Cartridge Azimuth?

Fozy meter......

melm, I hate to say it, but for stuff like this, the ears are woefully inaccurate.  To begin with, most of us do not have equal acuity in both ears, not to mention equal frequency response sensing, and not to mention room effects, etc.  And then there's the brain...
However, I also have no beef with just sitting the cartridge squarely at 90 degrees to the LP surface.  This is a recent and radical change of thinking for me.

1+ lewm

While setting up my Garrard today, my friend Rick had brought round his Fozgometer and test l.p. ( amongst other essential tools!) to be able to set azimuth.

I decided to just set it 90 degrees to the LP instead just as I always have done.
Maybe one day but I think I am close enough to enjoy the music as is.

@lewm 

For a long time I set it at horizontal and let it go at that.  Using an AT Art 9 I felt very comfortable with that, as the more expensive ATs are probably more carefully aligned than lower volume cartridges.  I was enjoying my analogs.  Using a VPI uni-pivot arm, setting at a true horizontal was as much work as I wanted to handle.

But when I got the dual pivot, I made a real discovery.  Using the long slender hex screwdriver that VPI used to include with their arms, I made the very slightest adjustment in azimuth (so easy to do) and was astonished at the results.  Fortunately it was in the correct direction.  It is such a small change that I can see no difference in its horizontal alignment, but I can surely hear the difference.

Interesting that I am at the moment working on improving the digital side of my listening.  After the very basics, trying to make it sound like analog, most of the refinement is exactly like setting azimuth, to wit, soundstage, width, depth, etc.  So my ears are well tuned to these things these days. They tell me everything I need to know.