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===Drift alignment method===
Drift alignment is a method to refine the polar alignment after a rough alignment is done. The method is based on attempting to track stars in the sky using the [[clock drive]]; any error in the polar alignment will show up as the drift of the stars in the eyepiece/sensor. Adjustments are then made to reduce the drift, and the process is repeated until the tracking is satisfactory.
{{Cleanup rewrite|Wikipedia is not a manual|section|date=July 2016}}
Two stars are needed for drift alignment, one for adjusting the azimuth of the mount, and one for adjusting the altitude of the polar axis (i.e. the 'latitude' setting). For the azimuth adjustment, one typically attempts to track a star close to the meridian (declination less than 30 degrees from the equator) in the hemisphere opposite of the observing ___location. For the polar axis altitude adjustment, one can attempt to track a star low in the east or west.
A rough alignment is performed, then refined by pointing at different stars and observing any drift that occurs. The mount is then adjusted according to the direction of the observed drift.
The procedure is as follows (hemisphere independent):
'''Step 1''' Point the telescope at a star in the meridian opposite the pole ___location (e.g. in the North from the Southern hemisphere) that has a declination less than 30 degrees from the equator.
'''Step 2''' Rotate the guider CCD or reticule eyepiece in the telescope so that moving the mount in Right Ascension causes the star to follow a crosshair line very accurately. Consider this line to be the ‘horizontal’. If the mount’s tracking is switched off for a few minutes the star should follow this line.
'''Step 3''' Position the star exactly on the centre of the cross hairs.
'''Step 4''' Leave the mount tracking and note the drift direction of the star away from the crosshair centre.
'''Step 5''' While watching the position of the star, put a hand on the '''front''' of the scope and push gently either up or down - enough to move the star visibly.
Figure out if you need to push UP to re-centre the star or DOWN.
'''Step 6''' If you need to push UP, use the azimuth adjustment to rotate the whole mount with the side facing the pole in the direction EASTward (imagine looking at the mount from above).
If you had to push DOWN, rotate the side of the mount facing the pole WESTward.
Start with a small rotation to get a sense of how much change the rotation will produce.
'''Step 7''' Go back to step 3. Keep repeating steps 3 to 7 until the star does not drift up or down for at least 5 minutes.
(Remember, sideways drift is not important).
'''Step 8''' Now point the scope at a star low in the West.
'''Step 9''' Centre the star perfectly and let the mount track until a drift is observed.
'''Step 10''' Put a hand on the '''front''' of the scope and give a gentle push. If you have to push the scope UP to re-centre the star, then you must increase the angle that the polar axis makes with the horizontal. If you need to push DOWN then the angle must be reduced.
(It is probably wise to figure out which way the adjustment knobs move your mount in daylight before you do the actual drift alignment. It is quite easy to get confused in the dark and go the wrong way.)
If the Western part of the sky is obscured, perhaps by trees or a building, then use a star in the East. Use the same procedure as for the West, but '''reverse the correction'''. If you have to push the scope UP to re-centre the star, then you must decrease the angle that the polar axis makes with the horizontal. If you need to push DOWN then the angle must be increased.
You should then repeat the whole procedure until no drift is seen for 10–20 minutes.
== Equipment used in polar alignment ==
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