Azimuth and zenith Where did these terms come from? And why?
I've never understood why a simple term like Horizontal Tracking Angle which is descriptive of the angle a cartridge makes to the groove has become "zenith" in some people's view.
Ok, maybe Horizontal Tracking Angle is a mouthful, so lets call it HTA. At least it means something relevant to cartridge set up. Zenith is a meaningless term in this context. I suspect it was a term used by someone, a manufacturer or reviewer, maybe, looking to obfuscate, or distinguish their spiel from the usual obvious descriptors thereby associating a new term with their product or theory.
The zenith is the point in the sky directly above you. Zenith angle is a term derived from this astronomical use, and used now, for example, in describing an angle which a line perpendicular to a solar panel makes with the zenith when the panel is pointing directly at the sun (when the sun is at the zenith ie overhead relative to the panel. To use it with reference to cartridge alignment is total nonsense.
So what's to blame for this?
Well, someone decided that we needed a term to describe the angle, when viewed head on, that a cartridge makes with the record surface, (or alternatively, the angle the stylus is offset to the vertical due to misalignment in set up or manufacture.) They called this angle azimuth rather than, say, cartridge tilt angle or radial offset angle. I suspect this was derived from tape head alignment use, where the tape head is angled with respect to the tape surface.
To use the term for hifi use, the correct corresponding candidate would be HTA - the angle the cartridge makes with the groove, not the stylus or cartridge relative to a notional plane sited on a radius perpendicular to the record surface. However, we are now stuck with it. That doesn't mean we have to use the terminology instead of a more sensible and clearer terminology.
Which brings us back to zenith. Whoever decided on this was obviously intent on maintaining some sort of naming consistency with azimuth without any further thought. I suspect someone will coin altitude for SRA (Stylus Rake Angle) or VTA (Vertical Tracking Angle).
Then all that's left is nadir, which is the point we will then have reached.
