I believe that the term declination was used in error in this article. On any nautical navigation chart the difference between magnetic and true north is called “variation.” Declination has always been the angle from the horizon to a point higher into the sky.

Bob Nickelson
King and Queen Court House, Va.

While navigators use the term variation to avoid confusion with declination (which indeed has astronomical meanings), some groups of geologists use declination to describe the angle between true north and magnetic north. —Sid Perkins The article might have noted that compasses are used for aligning photovoltaic modules and solar-heating panels. If the actual declination at time of placement is not correctly implemented, the output of these valuable renewable-energy resources is negatively impacted.

David Sweetman
Dyer, Nev.

The statement that the North Celestial Pole “lies within 0.5° of Polaris” is incorrect, at least at this time. In 2008 the angular separation is closer to 42 arcminutes, and it will be after 2060 before the separation is under 30 arcminutes (0.5°).

David Stoltzmann
Bayport, Minn.

Polaris, the North Star, is almost, but not quite, within 0.5° of the Earth’s rotational axis, as we reported. The separation between the two actually is 42 arcminutes, or 0.7°. —S.P.