The Moon will pass last quarter phase, rising in the middle of the night and appearing prominent in the pre-dawn sky.
From Seattle, it will be visible in the dawn sky, rising at 01:56 (PDT) – 3 hours and 37 minutes before the Sun – and reaching an altitude of 26° above the south-eastern horizon before fading from view as dawn breaks around 05:13.
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 last quarter, it rises in the middle of the night and appears high in the sky by dawn. It sets at around lunchtime. More information about the Moon's phases is available here.
Observing the Moon at last quarter
Over coming days, the Moon will rise later each day, so that it is visible for less time before sunrise and rises less far above the eastern horizon before dawn. By the time it reaches new moon, it will rise at around dawn and set at around dusk, making it visible only during the daytime.
Its daily progress is charted below, with all times are given in Seattle local time.
|Altitude of Moon
|Direction of Moon
|07 May 2012||05:42||21:45||8°||south-west|
|08 May 2012||05:42||22:54||14°||south-west|
|09 May 2012||05:38||23:51||19°||south|
|10 May 2012||05:37||00:39||24°||south|
|11 May 2012||05:37||01:13||27°||south|
|12 May 2012||05:33||01:43||28°||south-east|
|13 May 2012||05:33||02:11||28°||south-east|
|14 May 2012||05:33||02:33||27°||south-east|
|15 May 2012||05:29||02:56||24°||south-east|
|16 May 2012||05:29||03:20||21°||east|
|17 May 2012||05:29||03:43||17°||east|
|18 May 2012||05:29||04:08||12°||east|
The exact moment of last quarter
The exact moment of last 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 last quarter moon can be observed at any time in the pre-dawn sky.
At the moment it reaches last quarter, the Moon's distance from the Earth will be 387,000 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 12 May 2012|
21 days old
All times shown in PDT.
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.
|12 May 2012||– Moon at Last Quarter|
|20 May 2012||– New Moon|
|28 May 2012||– Moon at First Quarter|
|04 Jun 2012||– Full Moon|
Simulated image courtesy of Tom Ruen.