Your guide to the night sky this month
All month
August represents the last chance to see brightening Comet C/2017 K2 PanSTARRS from the UK. The comet starts the month in southern Ophiuchus, ending August near the claws of Scorpius and continuing to brighten all the while before reaching perihelion in December.
Monday 1
The first opportunity to take our Deep-Sky Tour occurs in the first week of August before the bright Moon interferes. The second opportunity occurs starting on 20 August through to the end of the month. This month we’re looking at objects around Sagitta.
Tuesday 2
The mag. +5.8 planet Uranus appears just 1.3º north of mag. +0.2 Mars this morning. The pair are located about 20º above the eastern horizon at 02:30 BST (01:30 UT). Binoculars may give a view of dim Uranus.
Wednesday 3
Magnitude –0.3 Mercury is roughly 1º from mag. +1.3 Regulus on 3 and 4 August, making it a possible telescope target for daytime viewing. If you try, however, take care as the Sun will be just 18º to the west.
Thursday 4
The clair-obscur effects known as the lunar X and V will be visible on the terminator of this afternoon’s 42%-lit waxing crescent Moon. The effects will be formed around 19:20 BST (18:20 UT) when the Moon is just to the west of south in the daytime sky.
Sunday 7
With just a week to go before Saturn reaches opposition, this is the time to start noting the relative brightness of the planet’s rings compared to its disc. Over the next evenings, the rings will slowly brighten to a peak at opposition on 14 August.
Thursday 11
Moonwatch this month takes in the albedo feature Reiner Gamma, a bright swirl on the surface of Oceanus Procellarum. Unlike relief features, which require oblique lighting to see at their best, albedo features are best seen around full Moon.
Friday 12
The full Moon lies 5.1º south of mag. +0.3 Saturn in the early hours of this morning. Catch the pairing as darkness falls on 11 August until closest just before moonset at 05:30 BST (04:30 UT) on 12 August.
Saturday 13
This morning plays host to the peak of the Perseid meteor shower. However, the presence of a just-past-full Moon in Aquarius will render this year’s visual peak unfavourable.
Sunday 14
The planet Saturn reaches opposition today, a time when its rings should appear at their brightest due to the so-called ‘opposition effect’.
Monday 15
This morning’s 87%-lit waning gibbous Moon lies 6º from mag. –2.6 Jupiter.
Friday 19
Magnitude 0.0 Mars sits 5.7º south of the Pleiades open cluster this morning. As the sky begins to brighten, the last quarter Moon will also be nearby, sitting a fraction less than 4º from Mars.
Saturday 20
A 41%-lit waning crescent Moon,
magnitude 0.0 Mars and the Pleiades form an isosceles triangle this morning, an attractive sight if you have clear skies.
Tuesday 23
Minor planet 4 Vesta reaches opposition at mag. +6.0. For more details and a full chart, see our Comets and Asteroids section.
Thursday 25
A 4%-lit waning crescent Moon sits 3º north of the Beehive Cluster, M44, very low above the east-northeast horizon just before dawn. View from around 04:00 BST (03:00 UT). 40 minutes later, mag. –3.8 Venus appears.
Friday 26
A 1%-lit waning crescent Moon lies 4.5º northeast (left as seen from the UK) of mag. –3.8 Venus this morning. Catch them together from 05:00 BST (04:00 UT).
Sunday 28
Catch a very thin and beautiful 2%-lit waxing crescent Moon low above the west horizon just after sunset this evening. The Moon sets approximately 50 minutes after the Sun.
Family stargazing
Noctilucent clouds (NLCs) are excellent targets for youngsters to look out for. Typically seen 90–120 minutes after sunset low above the northwest horizon, or a similar time before sunrise low above the northeast horizon, they just require a flat, clear horizon and keen eyes. They shine with a white/blue-white colour and have a fine wispy structure. Any regular clouds in the area will appear dark against NLCs – high altitude ice-sheet clouds, which are so high that they can reflect sunlight at night even though the Sun is below the horizon for us on the ground. bbc.co.uk/cbeebies/shows/stargazing
NEED TO KNOW
The terms and symbols used in The Sky Guide
Universal Time (UT) and British Summer Time (BST)
Universal Time (UT) is the standard time used by astronomers around the world. British Summer Time (BST) is one hour ahead of UT
RA (Right ascension) and dec. (declination)
These coordinates are the night sky’s equivalent of longitude and latitude, describing where an object is on the celestial ‘globe’
Naked eye
Allow 20 minutes for your eyes to become dark-adapted
Photo opp
Use a CCD, planetary camera or standard DSLR
Binoculars
10×50 recommended
Small/ medium scope
Reflector/SCT under 6 inches, refractor under 4 inches
Large scope
Reflector/SCT over 6 inches, refractor over 4 inches
GETTING STARTED IN ASTRONOMY
If you’re new to astronomy, you’ll find two essential reads on our website. Visit http://bit.ly/10_easylessons for our 10-step guide to getting started and http://bit.ly/buy_scope for advice on choosing a scope