the initial astrometry calibration for a telescope Generally a telescope can memorize how to point to a target with a particular RA&amp;Dec. There is no need to calibrate every day.
How can it happen?
How to let the telescope(non-amateur) know the position of a star after it was built? For an amateur telescope, how to realize it? There should be a zero point? 

How often should the calibration be?
First you have enter your coordinates into the mount's software and then align it(e.g. 3 star alignment).After having done that, when you finish the observation you have to park the telescope.

Actually Colin's answer is really helpful.They keyphrase is "After installation set up".
The whole procedure should be explained in your telescope's manual.
If you tell us which model you have we might be able to help more.