May Moon & Planet data for 2013


Phases of the moon (times as shown by guide)

Last quarter:  May  2 at 11.14 pm NZST (11:14 UT)
New moon:      May 10 at 12.28 pm NZST (00:28 UT)  eclipse of Sun
First quarter: May 18 at  4.35 pm NZST (04:35 UT)
Full moon:     May 25 at  4.25 pm NZST (04:25 UT)  RASNZ conference dinner
Last quarter   Jun  1 at  6.58 am NZST (May 31, 18:58 UT)

Solar eclipse.

An annular eclipse of the Sun will occur on the morning of May 10. The path of annularity starts at dawn in Australia, its path to the east taking it across York Peninsula where it crosses the path of the 2012 total eclipse. The subsequent northerly loop across the Pacific of this year’s eclipse takes the path away from New Zeland.

Only a very slight partial eclipse of the Sun will be visible from the North Island and the north and west of the South Island of New Zealand. At its greatest some 14% of the solar disk will be covered by the moon as seen from North Cape. The time of maximum eclipse as seen from New Zealand ranges from 11.40 am to noon. No eclipse will be visible from the aoutheast of the South Island south of about the mouth of the Clarence.

More details of the eclipse can be found on the RASNZ web site: < http://www.rasnz.org.nz/Eclipses/2013Eclipses.shtml#Sun1>

The planets in May

At the end of May, four of the naked eye planets will be in Taurus – along with the Sun. Only Saturn will be readily observable, by the end of May it will transit and so be highest to the north at 10 pm.

Planetary conjunctions

Venus, Mercury and Jupiter form a varying cluster of planets towards in the latter part of May with a series of mutual conjunctions. The conjunctions will all be difficult to see in the evening with the three planets setting no more than an hour after the Sun.

On the 24th Mercury will be at its closest to Venus, 1.4° below the brighter planet. Jupiter will be 4.6° away to the upper right of Venus.

Three evenings later, on the 27th, Mercury will be at its closest to Jupiter, but in fact still a little closer to Venus. The three planets will form a small triangle with Jupiter at the apex. Venus will be 1.8° below and slightly left of Jupiter. Mercury will be 2.4° below and to the right of Jupiter and 2.0° to the right of and very slightly lower than Venus.

The following evening Venus will be almost directly below and 1.1° from Jupiter, with Mercury 2.5° to the right of Venus and a shade higher.

Half an hour after sunset Venus will be about 3.5° above a sea level horizon, so very low. At magnitude -3.9 it should be readily visible in a clear sky. Jupiter a little higher is 2 magnitudes fainter while Mercury is at -0.6. All should be visible in binoculars.

Planets in the evening sky.

MERCURY in fact starts May in the morning sky. On the 1st it will rise just over an hour before the Sun. Half an hour later the planet will be about 5° above the horizon a little to the north of east. At magnitude -1 it may be visible in binoculars. Mercury will steadily get lower in the sky each following morning so becoming lost to view in the brightening sky after a few days.

On the morning of the 12th Mecury is at superior conjunction with the Sun. After conjunction the planet becomes an evening object. By the end of the month it will set just over an hour after the Sun. On the 31st Mercury will be about 5° up half an hour after sunset, with the planet, magnitude -0.4, to the northwest.

During May, Mercury moves across Aries and Taurus as it passes first Mars and then Venus and Jupiter. The conjunction with Mars occurs with the planets too close to the Sun to see. On the last evening of May, Mercury will be poised to move on into Gemini.

VENUS is an evening object throughout May. On the 1st it will set only 25 minutes after the Sun. This increases to an hour later by the end of May. By then it should be visible low in the north-westerly sky soon after sunset.

On the 31st, Venus will be a little less than 4° above the horizon half an hour after sunset. Jupiter will be 2.5° to its left and slightly lower, while Mercury will be 3.7° to its right and slightly higher.

Venus starts May in Aries, but moves on into Taurus on the 4th.

JUPITER sets just about 2 hours after the Sun at the beginning of May and 55 minutes later than the Sun on the 31st. So it will be a low object to the northwest as the evening sky darkens.

On the 12th a very thin crescent moon, only 4.5% lit will be 4.5° to the left of Jupiter. Three quarters of an hour after sunset the two will be about 7° up with Jupiter near northwest.

Jupiter is in Taurus all month.

SATURN was at opposition at the end of April so becomes a well placed evening object during May. At the end of the month it will be due north and highest in the sky close to 10 pm. The planet will starts May in Libra but its slow retrograde motion takes it back into Virgo on the 14th. It will be about midway between Spica mag 1.1 and beta Lib, mag 2.6. When highest in the sky the three will form a nearly horizontal line high to the north.

The moon and Saturn are in conjunction a couple of days before the moon is full. Early in the evening of the 23rd, the 95% lit moon will be to upper right of Saturn.

MARS will be the only planet in the morning sky all month but remains difficult to see. It rises only 15 minutes before the Sun on the 1st increasing to 48 minutes earlier on the 31st. At magnitude 1.4 it is not likely to be visible to the eye.

Outer planets

URANUS rises about 4.30 am at the beginning of May, two hours earlier by the end of the month. It will be in Pisces near a corner of Cetus at magnitude 5.9.

NEPTUNE rises 3 hours before Uranus, so shortly before midnight by the end of May. The planet is currently in Aquarius with a magnitude 7.9 during May.

Brighter asteroids:

Both (1) Ceres and (4) Vesta move across Gemini during May. Vesta at magnitude 8.4 is a little brighter than Ceres. By the end of May they will set about 2.5 hours after the Sun. Ceres will then be approaching beta Gem, magnitude 1.2. It is 3° from the star on the 31st. Vesta will be 8° “behind” Ceres.


Diary of events in May

The follwing table lists various solar system object events during May. A list of astronomical terms used in may be found after the table.

May 2 Moon last quarter
May 4 Neptune 5.6 degrees south of the Moon
May 6 Uranus 3.8 degrees south of the Moon
May 7 Mercury 0.4 degrees south of Mars
May 9 Mars 0.4 degrees south of the Moon Occn
Mercury 0.3 degrees south of the Moon Occn
May 10 Moon new Eclipse
May 11 Venus 1.4 degrees north of the Moon
Aldebaran 3.4 degrees south of the Moon
Mercury superior conjunction
May 12 Moon northern most declination (20.2 degrees)
Jupiter 2.5 degrees north of the Moon
May 13 Moon at apogee
May 17 Venus 5.8 degrees north of Aldebaran
May 18 Moon first quarter
Regulus 5.6 degrees north of the Moon
May 22 Spica 0.1 degrees south of the Moon Occn
May 23 Saturn 3.5 degrees north of the Moon
May 24 Mercury 1.4 degrees north of Venus
May 25 Moon full
May 26 Moon at perigee
Moon southern most declination (-20.2 degrees)
May 27 Mercury 2.3 degrees north of Jupiter
Pluto 0.9 degrees south of the Moon Occn
May 28 Venus 1.0 degrees north of Jupiter
May 31 Neptune 5.6 degrees south of the Moon
Moon last quarter
  • apogee: Furtherest point in the orbit of a body orbiting the Earth
  • declination: 'Latitude' for celestial objects. The distance in degress above (north) or below (south) the celestial equator.
  • perigee: Nearest point in the orbit of a body orbiting the Earth
  • superior conjunction: Conjunction where the Sun is between the Earth another solar system object