Monthly Skywatchers' Page

For London and the UK

Sun And Nine Planets
The Sun and eight major planets (plus KBO Pluto) to scale. Earth is third planet from the left.


Introduction

The location of the stars and constellations can be learnt throughout a single year from books, mobile phone applications or planetarium software. Each month of the year, the same stars are visible from a given location. Different stars and constellations are visible as the year progresses. For example, in London, the constellation of Orion is always visible in the evenings of winter months of January and February. Scorpius is visible in the summer months of June and July around midnight.

The planets resemble stars except that, generally, they do not twinkle. Unlike the stars whose patterns are fixed, planets wander through the sky changing their positions amongst the starry background. This means that their periods of visibility change as the relative position of the Earth, Sun and planet vary. In one year Mars may be visible in August at midnight. In another year it may be behind the Sun and invisible from Earth during August.

This page gives the details of visibility for the five naked eye planets: Mercury, Venus, Mars, Jupiter and Saturn. It also gives information about comets, meteor showers and non-regular phenomena like eclipses, transits and occultations.

The Observers' Glossary explains the terms used. Alternatively run the mouse cursor over terms in maroon.


The descriptions below are for viewers in the Northern Hemisphere, especially London and the United Kingdom.
The planetary information is valid for any location at the same or similar Latitude (51.5°N).
Note that a degree in the sky is twice the apparent diameter of the Moon.

All times on this page are London (UK) times. This is normally GMT (Greenwich Mean Time also known as Universal Time).
In the United Kingdom, the clocks go forward by one hour for British Summer Time (BST) between mid March and late October.
A 24 hour clock is used so that 7pm is written 19:00.


July 2017

Mercury

Mercury

Mercury is theoretically an evening object for the whole of this month.

Unfortunately, the planet sets just one hour after the Sun and is very low down. In addition, the twilights are very long at this time of year. The planet may perhaps be spotted using binoculars after the Sun has set.

The best day to look for Mercury may be the 25th when the very thin crescent Moon will be to the left of the planet.

Mercury and the Moon
Looking to the North of West at 9:30pm on 25th.
Mercury can be seen to the right of the thin crescent Moon.
With a pair of binoculars, the star Regulus may be spotted close to and above the planet.

Venus

Venus

Venus is a brilliant morning object rising more than two and a half hours before the Sun at the beginning of the month. The planet is visible among the stars of Taurus and to the right of the Pleiades star cluster.

Between the 8th and 13th Venus will be seen between the Pleiades and Hyades star clusters close to the star Aldebaran.

On 20th the old crescent Moon will be visible to the right of Venus.

By the end of the month the planet will be rising three hours before the Sun.

Venus and the Moon
Looking East at 3:30am on 20th.
The brilliant Venus can be seen to the left of the crescent Moon.
The star Aldebaran and the Hyades are to the right of the Moon. The Pleiades star cluster is above.

Mars

Mars

Mars is in conjunction with the Sun on 27th. The planet will remain too close to the Sun to be visible until September.

Jupiter

Jupiter

Jupiter is a brilliant evening planet among the stars of Virgo above that constellation's brightest star, Spica.

On 1st the planet sets around three and a half hours after the Sun and can be seen to the right of the Moon. By the end of July Jupiter will be setting about two hours after the Sun and will start to become lost in the evening twilight.

Jupiter is close to the Moon on 1st and again on 28th.

Jupiter and the Moon
Looking South of West at 10pm on 28th.
Brilliant Jupiter can be seen bellow the Moon.
Spica, can be seen to the left of the planet while Porrima is to the right of the Moon.

Saturn

Saturn

Saturn was at opposition last month is still visible for most of the night. By the end of July, the planet will be setting around 1:30am.

The planet is among the stars of Ophiuchus, a constellation ignored by astrologers. This places Saturn well South of the equator this year so the pale yellow, star-like planet does not rise very high from UK latitudes.

Look for the planet below the Moon on 6th.

Through a telescope the magnificent rings are easy to see and this year they are at an open angle. If you have access to a telescope, use the Moon to locate Saturn and look at it through a telescope on a clear night. The sight of the rings is one of the best views in the sky. During 2017, we are looking down onto the planet's North Pole so the rings appear to be wide open. The rings are open wide every fifteen years.

Saturn and the Moon
Looking South at 10:00pm on 6th.
Saturn is just below the Moon and to the left of the stars of Scorpius.

Sun

The Sun

After the Solstice on 21 June, the days have begun getting shorter, slowly at first. At the beginning of July the length of the day is 16 hours 32 minutes. By the end of the month this has reduced to 15 hours 26 minutes, a loss of 1 hour and 6 minutes of daylight.

During July, the time of local midday (when the Sun is at its highest in the sky and exactly due South) is just after 13:00 (remember we put the clocks forward in March). This makes the evenings slightly lighter than the mornings.

At 21:11 on 3 July the Earth will be at its furthest from the Sun (Aphelion). The Earth's motion around the Sun is then at its slowest. This is one of the reasons why the times of sunrise and sunset are asymmetrical and why the time of midday varies throughout the year.

At aphelion, the Sun's distance from the Earth is 152.1 million km (94.5 million miles). This compares to 147.1 million km (91.4 million miles) in early January when the Earth is at its closest to the Sun. This is a difference of some 5 million km. The further Sun gives the Northern Hemisphere summer 7% less heat than it would otherwise receive from the Sun.

The Sun's distance from the Earth does not cause the seasons. These are caused by the Earth's axis being tilted at an angle of 23.5° to the plane of its orbit around the Sun. It is the tilt that causes both the length of the day and the noon day altitude of the Sun to vary throughout the year. It also causes the seasons to be reversed in the Southern Hemisphere.

The Earth's changing speed around the Sun does have one effect. It makes the length of the four seasons different. The Earth is travelling at its slowest around the Sun between April and October and at its fastest between October and April.

In the Northern Hemisphere the lengths of the seasons are:

Spring 92 days 19 hours
Summer 93 days 15 hours
Autumn 89 days 19 hours
Winter 89 days 01 hour

The time of midday moves forward from 13:04 to 13:06 during July. Remember the clocks are forward at this time of the year. Around 26th, midday will be at 13:07, its latest value for the year.

The Sun begins the month in Gemini and enters Cancer on 20th.

Note that the Zodiac dates do not tie in with astrology as astrologers are using dates from two thousand years ago.

Date Sunrise Midday Sunset Length of Day Sun's Noon Altitude Notes
30-Jun
04:47
13:04
21:21
16h 33m 
61.6°
Moon close to Jupiter
01-Jul
04:47
13:04
21:20
16h 32m
61.6°
Evening Half Moon - Moon close to Jupiter
02-Jul
04:48
13:04
21:20
16h 31m
61.5°
 
03-Jul
04:49
13:04
21:19
16h 30m
61.4°
Aphelion (Earth furthest from the Sun) at 21:11
04-Jul
04:49
13:04
21:19
16h 29m
61.3°
 
05-Jul
04:50
13:05
21:18
16h 28m
61.2°
 
06-Jul
04:51
13:05
21:18
16h 26m
61.1°
Moon close to Saturn
07-Jul
04:52
13:05
21:17
16h 25m
61.0°
 
08-Jul
04:53
13:05
21:17
16h 23m
60.9°
 
09-Jul
04:54
13:05
21:16
16h 21m
60.8°
Full Moon at 04:07 ("in" Sagittarius)
10-Jul
04:55
13:05
21:15
16h 20m
60.7°
 
11-Jul
04:56
13:06
21:14
16h 18m
60.5°
 
12-Jul
04:57
13:06
21:13
16h 16m
60.4°
 
13-Jul
04:58
13:06
21:13
16h 14m
60.3°
 
14-Jul
04:59
13:06
21:12
16h 12m
60.1°
 
15-Jul
05:01
13:06
21:11
16h 10m
59.9°
 
16-Jul
05:02
13:06
21:10
16h 07m
59.8°
Morning Half Moon
17-Jul
05:03
13:06
21:09
16h 05m
59.6°
 
18-Jul
05:04
13:06
21:07
16h 03m
59.4°
 
19-Jul
05:06
13:06
21:06
16h 00m
59.3°
Final 16 hour day
20-Jul
05:07
13:06
21:05
15h 58m
59.1°
Moon close to Venus
21-Jul
05:08
13:06
21:04
15h 55m
58.9°
 
22-Jul
05:10
13:06
21:03
15h 52m
58.7°
 
23-Jul
05:11
13:06
21:01
15h 50m
58.5°
New Moon at 09:46 ("in" Cancer)
24-Jul
05:12
13:07
21:00
15h 47m
58.3°
9pm sunset
25-Jul
05:14
13:07
20:58
15h 44m
58.0°
Moon close to Mercury
26-Jul
05:15
13:07
20:57
15h 41m
57.8°
Latest time of midday
27-Jul
05:17
13:07
20:56
15h 39m
57.6°
Mars in conjunction with the Sun
28-Jul
05:18
13:07
20:54
15h 36m
57.4°
Moon close to Jupiter
29-Jul
05:19
13:06
20:53
15h 33m
57.1°
 
30-Jul
05:21
13:06
20:51
15h 30m
56.9°
Evening Half Moon
31-Jul
05:22
13:06
20:49
15h 26m
56.6°
 

Moon

The Moon

The Moon will be close to Jupiter on 1st and 28th.

The Moon will be close to Saturn on 6th.

The Moon will be close to Venus on 20th.

The Moon will be close to Mercury on 25th.


It is easy to depend on astronomy or CMMS software to perform daily computational activities and to keep track of data. Astronomy enthusiasts can choose from a wide variety of software options, while facility managers may have fewer options if they require CMMS software for their business.


Next Month

Jupiter and Saturn in the evening. Venus in the morning. Eclipses of the Sun and Moon.


All times on this page are London (UK) times.

Sources: Astronomy Now magazine, Cybersky, Starry Night Pro, USA Naval Observatory and UK Nautical Almanac Office.

© 2017 KryssTal
All sky images by Starry Night Pro Plus 6
Eclipse predictions (maps) courtesy of Fred Espenak, NASA's GSFC


Books From Amazon.co.uk


Observers' Glossary

An explanation of the terms used by sky observers. Includes descriptions of how the objects of the solar system behave in the sky as seen from Earth (especially the Northern Hemisphere high latitudes).


KryssTal Related Pages

Tables and data about the Sun, Earth, Moon, planets, asteroids and comets. All terms used are explained.

An account of how various properties of stars can be measured by studying starlight. Includes brightness, distance, luminosity, temperature, mass, radius, density and an introduction to the H-R Diagram.

A table containing a list of the 20 brightest stars in the Earth's sky. Explanations of all the associated terms like magnitude, spectral type and radial velocity.

A detailed account about eclipses, transits and occultations. These are irregular phenomena that can be observed in the sky. Includes eclipse trips around the world with photos and well as photos of recent transists of Mercury and Venus.

An easy-to-understand scaling of the Universe in space. Distances in space are represented by the time light takes to travel there.

An easy-to-understand scaling of the Universe in time. The chronology of the Universe is compared to a real year.

How humanity came from believing Creation Myths to postulating the Inflationary Big Bang Theory. The key stages in our understanding of our place in the cosmos and the people who broadened our understanding.

What do we mean by the words day, week, month, year? Who invented our calendar? When did the third millennium begin? The relation between time and astronomy.

The force that moves apples and planets. A short introduction to the ideas of Kepler and Newton that culminated with the theory of Universal Gravitation.

A look at the mathematics of a sphere with a section on sundials and the equation of time.


External Skywatching Links

These links will open in a separate window

StarDate Online
An excellent online skywatchers' magazine featuring detailed monthly information about astronomical events.

Astronomy Picture of the Day
A different image each day with an extensive archive and explanations.

Society for Popular Astronomy
Monthly planet and star gazing details with maps for young people.

Telescope House
A London based source of astronomical equipment, telescopes, software, maps and books.

Southern Sky Watch
Sky watchers information for the southern hemisphere.

Starry Night Pro
Superb planetarium software. Simulate the sky from anywhere on the Earth and any time.