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Lewis,
Simple surveyors trick: think of the scope as a theodolite. You could use the telescope itself but the magnification is far too great - 6-9X as per the average finder is perfect for this.
Years ago when i lived with a big garden, having got the mount aligned I set the mount so the dec axis was precisely horizontal (using a bubble level) then swung the OTA down (ie rotate the dec axis) till I could see the top of the fence in my finderscope*.
Waving handsignals at my devoted chain-man (wife) who was at the fence, she was able to put a mapping pin (a nail will do) at the spot indicated by the finders crosshairs.
Next time you set up the mount, to set the azimuth accurately look through the finder and rotate the mount in azimuth until the nail is on the finder crosshairs.
This assumes the mount is in the same spot each time, and the finder crosshairs and telescope have been accurately aligned.
BTW I worked a chainman in my student days, fun job...
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