The Moon will pass first quarter phase, appearing prominent in the evening sky and setting in the middle of the night.
From Seattle , it will become visible around 21:09 (PST), 16° above your south-western horizon, as dusk fades to darkness. It will then sink towards the horizon, setting 2 hours and 36 minutes after the Sun at 23:25.
At this time in its monthly cycle of phases, it appears almost exactly half illuminated.
As it progresses through this cycle, it is visible at different times of day. At first quarter, it appears high in the sky at sunset before sinking towards the horizon and setting in the middle of the night. More information about the Moon's phases is available here.
The exact moment of first quarter
The exact moment of first quarter is defined as the time when the Moon's ecliptic longitude is exactly 90° away from the Sun's ecliptic longitude, as observed from the center of the Earth. However, the Moon does not appear in any way special at this instant in time, and a first quarter moon can be observed at any time in the evening sky.
At the moment it reaches first quarter, the Moon's distance from the Earth will be 402,000 km. Its celestial coordinates will be as follows:
|Object||Right Ascension||Declination||Constellation||Angular Size|
The coordinates above are given in J2000.0.
|The sky on 08 December 2021|
4 days old
All times shown in PST.
The circumstances of this event were computed using the DE430 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.
|29 Jul 1990||– Moon at First Quarter|
|06 Aug 1990||– Full Moon|
|13 Aug 1990||– Moon at Last Quarter|
|20 Aug 1990||– New Moon|
Simulated image courtesy of Tom Ruen.