Good stuff so far.
Welcome to miroslav!
You definitely need a calibration tape from MRL or TEAC. Unfortunately that is one costly thing you can’t do without.
I listed a few things in the threads below some time ago
Radio Shack keeps moving their links around (How do they stay in business ?)
And here is another O-scope
Can't find Winscope anymore. The people at archive.org should be shot for making robots retroactive. IMO, they either have it archived or they do not. Once they have it (which they did in this case) they should keep it. To freeze time... that's what they're for. It's down right un-American!
I've only used PC-based O-Scopes for a few years now. They do the trick for tape deck alignment.
One thing to add about using sync or repro heads. It depends on the design of the machine. As a rule the repro head is better, but Tascam broke that rule with a few of their decks. Machines like the 38 and 48, use the same part number for both sync and playback heads. So, you don’t get the same advantage by using the repro for playback as you would with a machine that has a specially designed Repro head.
In a private studio environment your calibration will hold for a long time. When getting a new/old machine I recommend doing a full align (usually needed, but not always). After that you will just check it maybe every six months to see that it is still right on. I go for three years never having to tweak anything.
Yeah, about azimuth... I just go by the scope. If it stays within spec you don't have to mess with it all the time. The surface of the head will change with wear, so it may need a bump now and then over the long term.