SkyEye

July 2018

Welcome to SkyEye, your guide to this month's celestial events.

The Calendar

There are two eclipses this month, beginning with a partial solar eclipse on 13 July and ending with a total lunar eclipse on 27 July. Red Mars comes to opposition on the same day as the lunar eclipse.

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Date Body Event
1
2
3
4 Mercury 0.4° south of the open star cluster M44 (known as Praesepe or the Beehive Cluster)
5
6 Moon last quarter
Earth aphelion
7
8
9 Venus 1.1° north of Regulus
10 Moon occultation of Aldebaran: visible from northcentral Russia, northern and central North America, and most of Greenland
11 Jupiter stationary point: retrograde → direct
12 Mercury greatest elongation east (26.4°)
134340 Pluto opposition
13 Earth, Moon partial solar eclipse
Moon new
Moon perigee
14 Moon 1.1° south of the open star cluster M44 (known as Praesepe or the Beehive Cluster)
Moon ascending node
15
16 Moon, Venus 1.6° apart
17
18
19 Moon first quarter
20 Mercury aphelion
21
22
23
24
25 Mercury stationary point: direct → retrograde
Uranus west quadrature
26
27 Mars opposition
Moon apogee
Earth, Moon total lunar eclipse
Moon full
Moon descending node
28
29
30 Earth Southern δ Aquariid meteor shower
31 Mars minimum distance from Earth

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.

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Sun GeminiCancer

Mercury CancerLeo

Northern hemisphere observers watch Mercury slide towards the horizon throughout the month before disappearing by the last week but those in the south see it continue to rise higher until greatest elongation east on 12 July. After this, Mercury slowly descends towards the western horizon but it remains on view from the southern hemisphere throughout the month. The closest planet to the Sun moves from direct to retrograde motion on 25 July.

Venus Leo

The southern hemisphere is the place to be to watch the evening star continue to rise ever higher above the western horizon. In contrast, Venus simply maintains its distance above the horizon when viewed from the north. Venus passes just a degree north of the first-magnitude star Regulus on 9 July and in the morning of 16 July, puts on a pleasing display with the waning crescent Moon.

Earth and Moon

Earth reaches its farthest point from the Sun on 6 July. The date of aphelion can range from 2 July to 6 July.

Bright moonlight on 30 July obscures the Southern δ Aquariid meteor shower.

On 10 July, the first-magnitude star Aldebaran is hidden behind the disk of the Moon. Another kind of occultation occurs on 13 July when the New Moon partially eclipses the Sun and arrives at perigee shortly afterwards. With less than six hours separating the New phase and perigee, expect perigean spring tides. A total lunar eclipse takes place two weeks later.

Mars Capricornus

Mars reaches opposition on 27 July, shining at magnitude -2.8. Superior planets are usually closest to Earth at opposition but due to the considerable eccentricity of the red planet's orbit, Mars is closest to Earth four days later. This is a particularly favourable opposition, as Mars is close to perihelion and Earth is close to aphelion, resulting in the two planets being only 0.385 au distant. Southern hemisphere observers can see Mars all night but due to its southerly declination, the red planet doesn't rise until midnight or afterwards for those in northern latitudes.

Jupiter Libra

Jupiter is now an evening sky object although it continues to favour southern latitudes. On 11 July it resumes direct motion, having been in retrograde since March.

Saturn Sagittarius

Now past opposition, the ringed planet is an evening sky object and best seen from southern latitudes.

Uranus Aries

Rising about midnight at the beginning of the month, Uranus reaches west quadrature on 25 July.

Neptune Aquarius

A small telescope is necessary to view the most distant planet in the solar system. It rises in the evening for southern observers but not until midnight or afterwards for those in the north.

The Celestial Sphere

Constellations are patterns of stars in the sky. The International Astronomical Union recognises 88 different constellations. The brightest stars as seen from the Earth are easy to spot but do you know their proper names? With a set of binoculars you can look for fainter objects such as nebulae and galaxies and star clusters or some of the closest stars to the Sun.

Descriptions of the sky for observers in both the northern and southern hemispheres are available for the following times this month. Subtract one hour from your local time if summer (daylight savings) time is in effect.

Local Time Mid-month Northern Hemisphere Equator Southern Hemisphere
1730 hours (1830 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S
1930 hours (2030 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S
2130 hours (2230 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S
2330 hours (0030 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S
0130 hours (0230 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S
0330 hours (0430 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S
0530 hours (0630 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S