The night sky in September 2020

The night sky in September 2020

Here is a map of the sky as it will appear from the latitude of London (51° 50′) in mid September, 2020, at 22h UT (GMT).

It is a helpful guide as part of our mission to help beginners to astronomy. If you are into stargazing but not already a member, you can join here, and be part of a great UK-based community.

The centre of the map shows the sky above your head, and your horizon is the circle running around the edge.

The sky appears the same at the start of the month at 23h UT and at the end of the month at 21h UT. To find out what is on view in this period, check out the latest Sky Diary from Popular Astronomy  (160 kB PDF).

The map is interactive, which means you can input your own location, date and time to check how the sky looks under different circumstances. (To do this, click on either the date or location to the top left of the map and then enter your own details in the window that appears).

If you’d like a description of this month’s sky, with more details about the constellations on view, then go to our Young Stargazers’ Sky Guide.

How and where to see Perseid meteors

How and where to see Perseid meteors

Perseid meteors are still visible up to 24 August so keep watching!

Stargazers are looking forward to the annual display of meteors (shooting stars) known as the Perseids. Dozens of bright meteors could be visible every hour in mid August – if you know when and where to look.

Each year the Earth ploughs through a stream of dust from the tail of comet Swift-Tuttle. The comet itself won’t return to the vicinity of Earth until 2126, but the dust particles from it have spread over a wide band all the way around its orbit. When the Earth encounters this dust stream, the tiny particles burn up in our upper atmosphere, giving rise to what look like shooting stars, known to astronomers as meteors.

Perseid meteor radiant
How the Perseid meteors could appear in a composite made over many minutes at about 11 pm on 12 August. Base image from Stellarium.

When to look for the Perseid meteors

In 2020, the night when maximum numbers occur is Wednesday to Thursday 12–13 August. But lower numbers can be seen for a week or two on either side of that date, and this is a good time of year for seeing meteors from other streams as well.

You can see the meteors from anywhere that has a good view of the sky, but ideally you need to be away from city lights. The darker the sky, the easier it is to see them. Although many of the meteors are as bright as the brightest stars, it’s easy to miss the fainter ones if your skies are not dark.

The meteors radiate away from the constellation of Perseus, in the north-eastern part of the sky in the evening. This lies just below the well-known W-shaped star pattern of Cassiopeia. But if you want to see the more spectacular meteors, it’s best to look away from that area, so as to see the longest streaks as they dash across the sky. Experts recommend looking about 40º away from this radiant point, and about 50º up in the sky, which is about the mid-point between the ground and the overhead point. So viewing to the north-west, around the Plough, or to the south, above the bright planets Jupiter and Saturn, is a good bet.

How many will I see?

Sky guides usually quote a figure known as the Zenithal Hourly Rate, or ZHR. This is the number that an attentive observer who hasn’t fallen asleep would see in perfect skies with the radiant point directly overhead. But from the UK the radiant won’t be overhead, and our skies are rarely perfectly dark. So the number will never be as high as the predicted ZHR. This year, ZHR figures of between 80 and 150 have been quoted, but in reality you are more likely to see about half those numbers even in the early morning when the radiant is at its highest.

Although Perseus is in the sky as soon as it gets dark, about 10:30 pm BST, it is very close to the horizon, so that cuts the number down considerably. And by about 1 am, when the radiant is a bit higher, the waning Moon starts to rise and brightens the sky. Even so, observers are expecting to see plentiful numbers. Also bear in mind that meteors are completely random, so they don’t come along in a regular stream. You could go for ten minutes or more without seeing a single one, then there could be two in quick succession. The secret is to be patient and alert all the time – not always easy at 2 am!

For more information on the Perseids and how to observe meteors, visit our Meteor Section site. And if you found this page useful, do think about joining the SPA – we offer fantastic value for money and we really do believe in stargazing for everyone!