This ornamental metal armillary in a silver nickel plated finish has a spherical framework of rings, centred on Earth, and represent lines of celestial longitude
Astronomically, the Moon is new when it and the Sun have the same celestial longitude
The instant of new Moon occurs when our satellite's celestial longitude
(along the ecliptic) matches that of the Sun, and its date and time are given to the nearest minute in each issue of this magazine (see page 95).
He also reported that the gegenschein's center sometimes lags behind the antisolar point in celestial longitude
Taking both visual and radio data into account, they find that the peak probably occurred near 12h UT on June 27, 1998, when the Sun's celestial longitude
Today we usually mark the beginning of the seasons when the Sun's celestial longitude
passes 0u (spring), 90u (summer), 180u (autumn), and 270u (winter).