I agree with Mike, that phase is everything in azimuth adjustment -- however, from my reading of the Fozgometer instruction manual:
http://www.musicalsurroundings.com/Manuals/Fosgate/FozgometerManual.pdfit only measures L or R crosstalk levels (separately of course which is good) and L vs. R cartridge output levels (balance) AS MEASURED THRU YOUR PHONO PRE. I mention that little detail here because that fact makes it important to know if your phono pre is in perfect balance first! Now, that's easy enough to find out by running JUST the left OR right tonearm lead/signal thru one and then the other channel of the phono pre and making sure the output of each side (measured thru the tape output on your preamp) is the same. The Foz can balance the signal for you internally which is nice; otherwise, if any of the cartridge, the record, and/or the phono pre are not each in perfect balance, that CAN be adjusted with the preamp's balance control, EXCEPT you'll then have to take your readings from the preamp's main outputs, not the tape outputs. Just remember, results with the Foz or any measurement device depend on/assume the L and R signal are the same strength, whether your testing is crosstalk-based or phase cancellation-based.
It's recommended the Foz also be used with a test record -- one with which I am unfamiliar, so I don't know if it contains an out-of-phase mono track. The Cardas record does, and it was cut by Stan Ricker, the best in the business, so I would rely on its accuracy: i.e. that both channels are precisely cut at the same amplitude, AND that there is a minimum of left/right phase cancelling crosstalk in the grooves themselves.
Both measurement techniques -- crosstalk levels or degree of phase cancellation -- will provide dependable result if set up and carried out with good experimental technique ;--) however I prefer the phase cancellation method because I feel it's more precise (i.e. the cancellation is either complete, or it's not) while the crosstalk method involves some subjective judgement (as implied in the Foz manual.)
Yes, you can use an oscilloscope as your measuring device; and if you're measuring crosstalk, it's essential if you don't have a Foz. But if you have a Cardas (or other) test record with a L/R out-of-phase track, and a mono switch on your preamp, then any device (including your ears!) will do just fine ;--))
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