SkyEye

The Calendar

A spectacular total solar eclipse takes place on 2 July, with a partial lunar eclipse two weeks later. Saturn is at opposition early this month too.

The Solar System

The word planet is derived from the Greek word for 'wanderer'. Unlike the background stars, planets seem to move around the sky, keeping mostly to a narrow track called the ecliptic, the path of the Sun across the stars. Dwarf planets and small solar-system bodies, including comets, are not so constrained, often moving far above or below the ecliptic.

Sun Gemini → Cancer

Mercury Cancer → Gemini

Mercury experiences another short bout of retrograde motion this month, from 7 July to the last day of the month. It also reaches aphelion on 7 July. Visible in the west after sunset early in the month, it soon vanishes from view as it undergoes inferior conjunction on 21 July. It re-emerges in the east at dawn before the end of July.

Venus Taurus → Gemini → Cancer

The northern hemisphere may finally have a slight edge when it comes to viewing the morning star but Venus is low in the east before sunrise and despite its brightness (magnitude −3.9), it may vanish in the glow of the dawn sky before the end of the month, leaving the lunar occultation of 31 July unobserved.

Earth and Moon

There are two eclipses this month. The first, a total solar eclipse, occurs on 2 July. The second, two weeks later, is a partial lunar eclipse. Aphelion, the day when Earth is farthest from the Sun, is on 4 July. Finally, a meteor shower, the Southern δ Aquariids peaks on the penultimate day of the month. The waning crescent Moon should not cause any problems with observations of this shower.

Mars Cancer → Leo

As the Moon overtakes Mars on 4 July, our satellite actually occults the red planet in an event beginning around 03:15 UT. Four days later finds Mercury and Mars in conjunction, just over 4° apart in evening twilight. On 13 July, Mars is only 0.4° south of M44, Praesepe or the Beehive Cluster. This small planet is getting increasingly difficult to see in the western sky as it dims and draws closer to the Sun.

Jupiter Ophiuchus

Now past opposition, Jupiter is an evening sky object, not setting until after midnight. It dims slightly but still outshines every other celestial body in its vicinity. The best views of the gas giant, as has been the case all year, are from the southern hemisphere.

Saturn Sagittarius

Saturn finally reaches opposition on 9 July, just over six months since conjunction. It shines at a magnitude of +0.1 and exhibits a ring tilt of approximately 24°. One week after opposition, a Full Moon occults Saturn in an event beginning at about 05:00 UT. Saturn is visible most of the night but is low to the horizon when viewed from northern temperate latitudes.

Uranus Aries

A morning sky object, Uranus reaches west quadrature on 29 July. Planet watchers in the southern hemisphere have the best views as the dawn skies are brighter in the northern hemisphere this month.

Neptune Aquarius

A small telescope is necessary to view the most distant planet in the solar system and the southern hemisphere is the best place to be to try to observe Neptune this month. For these favoured locations, Neptune rises well before midnight but planet watchers in the temperate north must wait until after midnight to try to catch a glimpse of this elusive planet.