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Doug, it's all to do with precession.
The true SCP is always at dec -90, but astronomy uses coordinate systems fixed at various dates with B1950 and J200 being the most commonly seen. The coordinates would have to be precessed backwards to determine at what date they had dec -90 and hence were pointing at the true SCP.
As for jumping from RA 12 to RA 23, when you are that close to the pole tiny changes in position can cause large changes in RA while making little difference in dec.
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