Type the UT date and time in the first box below, and then press the 'calculate' button.

The program will calculate various parameters for the Moon at the instant You have chosen.


Type in the UT date and time:

Date format: the date 10 january 2014 at 20:40 is entered as 20140110.2040.

Enter UT date in yyyymmdd.hhmm format:    

Physical Ephemeris of Moon:

Selenographic longitudes towards Mare Crisium are taken as positive. All figures here are based on geocentric coordinates, and position angles relate to the North Celestial Pole.

Libration in Latitude (B):

Libration in Longitude (L):

Colongitude of the Sun (Co):

Subsolar point Lat (Bo):

Subsolar point Long (Lo):

Selenographic Longitude of terminator:

Illuminated fraction of Moon's disc:

Position angle of bright limb:

Position angle of polar axis:

Results: Time

Days since J2000.0:

Julian Day Number:

Results: Sun's position

Distance (AU):

Right Ascension:


Results: Moon's position

Distance (Earth radii):

Right Ascension:




This page works out some values of astronomical interest. The central formula for Moon position is approximate. Finer details like physical (as opposed to optical) librations and the nutations have been neglected.

Formulas have been simplified from J. Meeus (MEEUS J., “Astronomical Algorithms”, Wilman-Bell, 1991) chapter 51 (sub-earth and sub-solar points, PA of pole and Bright Limb, Illuminated fraction).

The librations figures are usually 0.05 to 0.2 degree different from the results given by Harry Jamieson’s “Lunar Observer’s Tool Kit” (a DOS software). Some of the code is adapted from a BASIC program by George Rosenberg (ALPO).

Please report any errors or inaccuracies.