Magnetic north on Shade corresponds to magnetic south on the majority of other planets.* It was a simple matter of someone choosing the other end of the needle, and results in maps being frequently held upside down among offworlders. Shade's magnetic core is reasonably stable, with no giant reversals within recorded history. The magnetic north pole meanders at a leisurely pace around the northern hemisphere.
Sidereal north was historically used as an approximation for north with reference to Lauvja ("The Lodger"), the northernmost bright star visible in Shade's sky [during the Twine Wars period]. Lauvja is in fact a fraction off true north and 'travels' around the pole once yearly, such that with better measurements, what's known as sidereal 'north' actually describes a circle around the (true) north pole. Lauvja is still useful for navigation in most of the northern hemisphere.
The radius of the 'sidereal circle' (also 'Lauvja's balcony', 'Lauvja's sea view', 'Lauvja's lunchtime stroll' etc) is approximately one-seventh of a half-circumference of the planet (that is, the sidereal circle extends one-seventh of the distance between the north and south poles overland. That's a bit smaller than the [earth's Arctic Circle]).
As a result, celestial north (which is geographic/true north as measured by the stars) is located using the relationship between Lauvja and other stars.