Thanks for the detailed response and insight. I understand the nature of the EQ geometry especially when pointing near meridian or zenith etc. (ie. dome azimuth offset from OTA azimuth)
I think some of the confusion comes from my use of the Foster Systems dome control package (AstroMC software). It's the only one I have any experience with. They have defined a "Sync to Scope" process to "align" the dome opening to the OTA. Here are their instructions:
"Move the dome so that the shutter is facing approximately due East or due West. Then move your telescope so that the OTA is centered in the shutter opening at an altitude of approximately 45 degrees. Then click SYNC-TO-SCOPE."
I assume they pick due east/west and 45deg Dec because this is one orientation where the dome and OTA azimuth would be the same?
What I'm not sure about is whether this Foster System Sync-to-Scope even applies if I have "AstroMC calculates Az" turned off (and SGP is set to slave the dome).
DaveNL