Dates and times are NZST (UT + 12 hours) from May 5 unless otherwise specified. Rise and set times are for Wellington. They will vary by a few minutes elsewhere in NZ.

Sunrise, sunset and twilight times in may

                       May  1  NZST                May 30  NZST
                    morning  evening                 morning  evening
            rise:   7.04am,  set:  5.30pm    rise:   7.33am,  set:  5.03pm
Twilights
  Civil:    starts: 6.38am,  ends: 5.57pm    starts: 7.05am,  ends: 5.33pm
  Nautical: starts: 6.06am,  ends: 6.30pm    starts: 6.31am,  ends: 6.06pm 
  Astro:    starts: 5.34am,  ends: 7.02pm    starts: 5.57am,  ends: 6.39pm

May phases of the moon (times as shown by guide)

  Full moon:     May  4 at  3.42 pm (03:42 UT)
  Last quarter:  May 11 at 10.36 pm (10:36 UT)
  New moon:      May 18 at  4.13 pm (04:13 UT)
  First quarter: May 26 at  5.19 am (May 25, 17:19 UT)

The planets in may

Mercury and Mars are both too close to the Sun to observe for a second month. Venus continues to get higher in the evening sky while Jupiter gets lower setting around 10 pm by the end of May, so is best observed early evening. Saturn is at opposition on May 23, so is best viewed late evening and early morning.

Mercury sets 45 minutes after the Sun on May 1. It is at its greatest elongation 21° east of the Sun on the 7th. Although it will then set 53 minutes after the Sun it will be too low for observation. It is at inferior conjunction between the Earth and Sun at the end of May. Mercury will then be about 2° south of the Sun with its unlit side towards the Earth. At conjunction Mercury will be 70 million km from the Sun and 82 million km from the Earth.

Venus sets 2 hours after the Sun on the 1st and 3 hours after it on the 31st. On May 1 Venus will be 13° up half an hours after sunset. The planet will be in Taurus some 3° above El Nath, beta Tau, at magnitude 1.7 the second brightest star in Taurus. Venus moves to the east into Gemini on the 8th. By the 31st, half an hour after sunset Venus will be 20° above the horizon to the north of northwest. It will then be 4° above Pollux, at magnitude 1.2 the brightest star in Gemini.

On the evening of May 21 the crescent moon, 11% lit will be 9° to the left of Venus. The following night the moon will be a similar distance above Venus.

Mars sets only half an hour after the Sun on the 1st. By the 31st this has reduced to only 10 minutes later. Conjunction occurs in mid June.

Jupiter will be best placed for viewing as the sky darkens following sunset. On the 1st it is highest, 31° and due north at transit, 6.49 pm. By the end of May, Jupiter transits at sunset and will be 30° up at 6pm an hour after sunset. Altitudes are for the latitude of Wellington. The planet will be a little higher further north and lower further south in NZ

The time Jupiter sets gets steady earlier during the month from a few minutes before midnight on the 1st to a few minutes after 10 pm on the 31st. It will be in Cancer rather distant from any bright stars. It will be moving slowly to the east in the direction of Regulus, but remain 15° from the star by the end of May.

Mutual events of jovian satellites

There are about 10 mutual events of Jupiter's Galilean satellites observable from NZ during May. Some occur very soon after sunset or when Jupiter is very low. Better placed one include:

May 3, Callisto occults Ganymede, mid event ca 10.40pm, duration 6.8 min, altitude ca 10° May 5, Io eclipses Europa, mid event ca 8.16pm, duration 5.3 min, magnitude change of Europa 1.5, so easy to detect May 13, Ganymede occults Io, mid event ca 6.07pm, duration 5.5 min May 17, Io occults Ganymede, mid event ca 8.12pm, duration 4.9 min May 20, Ganymede occults Io, mid event ca 9.05pm, duration 6.4 min May 25, Europa occults Io, mid event ca 6.28pm, duration 3.5 min May 27, Ganymede occults Europa, mid event ca 8.03pm, duration 7.3 min,

this occultation is total for about 90 seconds.

Useful observations and timings of these events can be made by those set up for the video observation of minor planet occultations.

Users of Dave Herald's Occult program can generate their own predictions of these and other events. Hristo Pavlov's Occult Watcher programme will also list them and has diagrams showing the satellites relative to Jupiter. Details can also be found on the IMCCE web site, <a href="http://www.imcce.fr/phemu/">http://www.imcce.fr/phemu/</a> where predictions and requirements for observing and reporting information are available.

Saturn is at opposition on May 23. It rises just over an hour after sunset on May 1 and about half an hour before sunset on May 31. The planet starts the month in Scorpius near beta1 Sco (mag 2.6). It moves slowly to the west through the stars during May, crossing into Libra on May 11.

At opposition on May 24, Saturn will be slightly less than 9 AU, 1341 million km from the Earth and 10 AU, 1493 million km from the Sun.

The almost full moon will be just under 4° to the left of Saturn on the evening of May 5. The two are closest about 4am on the morning of May 6.

At present Saturn's north pole is tilted 25° towards the Earth. This brings the northern surface of the rings well into view. They should be visible in binoculars, although a small telescope is likely to give a better view.

Outer planets

Uranus is a morning object in Pisces rising 2 hours before the Sun on the 1st and rather over 4 hours before the Sun on the 31st. The planet's magnitude is 5.9, so readily visible in binoculars

Neptune rise a little over 5 hours before the Sun on May 1. By the 31st it rises just before midnight. The planet remains in Aquarius at magnitude 7.9

Pluto is in Sagittarius rising near 9.30 pm on the 1st and 2 hours earlier on the 31st. Its magnitude is 14.3.

Brighter asteroids:

(1) Ceres is in Capricornus during May, its magnitude ranging from 8.9 to 8.5 through the month. It rises a little before 11 pm on the 1st and at 9 pm on the 31st.

(4) Vesta is a morning object in Aquarius for most of May, but moves into Pisces on the 29th. Its magnitude is close to 8.0 all month. Vesta rises at 2.20 am on May 1 and 1.20 am on the 31st.

Brian Loader  
New Zealand