Quote:
Originally Posted by astroron
That is my understanding, I only thought they went every 50 years?
FOR 99% of deep sky objects it doesn't matter, but thing like stars that have proper motion it does.
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Hi Ron,
No quite ...
The effects of precession and nutation of course are to do with the wobble
of the Earth's axis. Therefore,
all positions in the sky shift gradually and continually,
including nearby objects and those that are very far away, such as DSO's. In fact,
when only these effects are taken into account, the angular separation of these various objects
with respect to each other remains constant.
However, stars, a you know, also have 'proper motions' - they drift around within
galaxies and thus depending upon their velocities and whether they are moving
side-to-side with respect to us or toward or away from us and depending upon
how far from us they are will determine their relative proper motions. Different
stars will have different proper motions, hence their relative angular
separatons changes over time. As you also know, due to the expansion of the
Universe, galaxies are also moving over time but since the distances are so far
the angular change is extremely tiny.
However, with the Earth wobbling about and all these objects moving every
which away, it probably makes remembering where they all are pretty moot
if you could somehow manage to live for long enough.
Best regards
Gary