An official website of the United States government
Here's how you know
A .mil website belongs to an official U.S. Department of Defense organization in the United States.
A lock (lock ) or https:// means you’ve safely connected to the .mil website. Share sensitive information only on official, secure websites.

 

What is the Celestial Pole Offset?

The gravitational attraction of the Sun and Moon on the non-spherical Earth cause the rotational axis of the Earth to precess in space similar to the action of a top. In addition to this precessional motion the axis undergoes a small "nodding" motion called nutation. Both of these motions can be described theoretically to a high degree of accuracy. This mathematical description depends on assumed values of physical constants describing the shape and internal structure of the Earth. Observations indicate that small residual corrections are required to the currently adopted International Astronomical Union (IAU) model. These corrections are given in longitude (dpsi) and obliquity (deps), where longitude refers to the angle measured eastward along the ecliptic from the intersection of the two planes and obliquity is the angle between the plane of the Earth's orbit (ecliptic) and the equatorial plane.  
 
Navy.mil  |  Navy.com  |  Navy FOIA  |  DoD Accessibility/Section 508  |  No Fear Act  |  Open Government  |  Plain Writing Act 
USA.gov  |  Veterans Crisis Line  |  DoD Safe Helpline  |  Navy SAPR  |  NCIS Tips  |  Privacy Policy  |  Contact Webmaster
 
Commander, Naval Meteorology and Oceanography Command  |  1100 Balch Blvd.  |   Stennis Space Center, Mississippi 39529
Official U.S. Navy Website
Veteran's Crisis Line