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I think I'm understanding what Peter is getting at, but suspect others aren't? He seems to be suggesting a way of accelerating drift alignment by taking 2 images - one at where you would start drift aligning, the other at the end of drift aligning. Plate solving each image and comparing the difference in dec is effectively the same as watching a star drift off the dec axis like we do when drift aligning. No?
Alt - drift aligning you'd point somewhere above horizon and near celestial equator (dec around 0). Turn off dec guiding and watch over some time the stars drift off axis. Adjust alt until they remain on axis. With Peter's method you'd do the same thing, only you'd take one image, plate solve and note the centre of image dec. You'd slew in RA only some angle, Peter is suggesting 30 arcmins? Image and plate solve again. Compare the dec to previous, and any difference would surely be the same as if you'd watched a star drift off axis over the same time mount would go that angle in sidereal time. This would assume the plate solve is pretty accurate, and that the difference in atmospheric refraction over such small angle is negligible. You'd adjust alt until the difference in dec between the 2 images is acceptably low.
Az - same as above but instead of near horizon, you're near zenith and adjusting az knobs.
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