A very accurate polar alignment method that watches stars drift in declination. You adjust the axis in azimuth with a star near the meridian and the equator, then in altitude with a star low in the east or west. It takes patience but no polar scope.
ToolsPolar alignment
Related terms
- Drift
The slow sliding of a star across the field when tracking is not perfect. Drift in declination betrays imperfect polar alignment; drift in right ascension usually comes from the mount’s speed or gears. In imaging it stretches the stars.
- Polar alignment
The adjustment that points the polar axis of an equatorial mount at the celestial pole. Its angle above the horizon must equal your latitude (51.5° in London), and it must aim at true north, not magnetic north. Good polar alignment keeps stars from drifting, visually and in photos.
- Polar scope
A small scope built into the polar axis of an equatorial mount, with a reticle. Since Polaris is about 0.65° from the pole, you place it at a precise spot on the reticle that depends on the time. An app or calculator tells you where.
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