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The R.A. and Dec remain the same, but because things do move
over long periods of time, sky atlases have to be updated to show the new positions. Because of the large amount of work involved in updating, and also because the changes in position are not great, updates are generally carried out at 50 year intervals. We are now using epoch 2000.
Earlier atlases used epoch 1950, so as we move further past 2000 small
inaccuracies in the positions of the apparently faster moving objects
creep in. When the 2050 atlases are published the positions will be spot on again.
raymo
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