2025 August 2

Difficult Conditions for the Perseid Shower This Year

John Mason

With Full Moon occurring on 9^th August, observing conditions for the run up to Perseid maximum on the 12^th and for several other lesser showers occurring during that period will present something of a challenge for observers this year.

For the first few days of August with the First Quarter Moon quite low in the sky, observations of the complex of minor showers (now grouped together as part of the Antihelion Source) which peak in late July but remain quite active in early August, the Alpha Capricornids and Southern Delta Aquarids will be possible with relatively little interference from moonlight.  However, as we approach Full Moon on August 9, and for about a week thereafter, observations of the Perseids and the Kappa Cygnids will be hampered by bright moonlight.

The Perseids are one of the most reliable meteor showers of the year, producing an abundance of fast, bright meteors, many with persistent trains.  Dust grains from the Perseid shower hit Earth’s atmosphere at a speed of 58.6 km/sec – that’s about 131,000 mph!  In 2025, the Perseid meteor shower is expected to peak between 19h and 22h UT (20h and 23h BST) on Tuesday, August 12, in the early evening and as darkness is falling from the UK.  This means that for visual and video observers in the British Isles the late evening of August 12 and early morning hours of August 13 will probably produce the highest observed rates.  Radio observers, however, will be able to cover the peak itself.  (See paragraph below for more details.)  The shower peak is quite broad, however, so watches carried out across the two nights of August 11-12 and 12-13 are likely to yield moderate observed rates, but the bright moonlight will be a problem, swamping out all but the brighter meteors.

On August 9, when the Moon is Full, it will be low in the southern sky among the stars of Capricornus, so it should be fairly easy to position yourself with the Moon behind you and hidden behind a wall, tree or other suitable obstruction.  By August 12, with the waning gibbous Moon in Pisces (quite near Saturn in the sky) it will be more obtrusive, but again observers can minimise its effects by directing their view towards the northern sky, from Cassiopeia and Perseus across to Ursa Minor, Ursa Major and Boötes.  Positioning oneself on the northern side of the wall of a house or other tall obstruction and looking north will certainly help.

Unfortunately, high observed Perseid rates cannot be expected this year and observers should beware of some of the more sensational forecasts appearing in the popular press and on social media, many of these articles written by ChatGPT and the like.  By the time the Moon reaches Last Quarter on August 16, and located on the Aries/Taurus border, Perseid activity will be in decline but the kappa Cygnids, which produce slow but invariably bright trails, will be at their peak.  Rates are low however, typically no more than 5 meteors per hour.

When to observe

Observed Perseid rates improve as the radiant altitude increases from 27° at 21h, to 43° at midnight and 66° by 03h.  All else being equal, the best observed rates are found when the Perseid radiant is highest in the sky during the pre-dawn hours.  Near the radiant Perseid trails will tend to be short, whereas on the other side of the sky the meteors will appear as streaks with long paths.

UK-based observers watching after midnight on August 11-12 (Monday-Tuesday) should experience increasing activity towards dawn, as the shower radiant at RA 03h 11m, Dec. +58°, near the Double Cluster, on the Perseus-Cassiopeia border, climbs higher in the eastern sky. There should also be good activity the following night on August 12-13 (Tuesday-Wednesday).  Although few in number, Perseids seen in the evening when the radiant is low will last longer and travel a much greater distance across the sky than those observed in the early morning hours.  Some of these ‘earth-grazing’ Perseids can be spectacular if they happen to pass more or less overhead.

It is hoped that, weather permitting, observers will cover shower activity even on nights away from the maximum, for example on August 10-11 and 13-14.

Visual observing

A naked eye visual meteor watch requires the minimum of equipment, even for more experienced observers. Ideally, one needs to find a site away from artificial lights, and recline on a deckchair or similar support so that the sky at 50° altitude can be watched in comfort, taking account this year of the need to minimise the effects of bright moonlight as far as possible. Appropriate clothing is essential as it can get quite chilly even on summer nights!  An accurate timepiece, a dim red torch, notepad or clipboard with report forms, and several pens and/or pencils are the only other needs. Alternatively, you can record the details of every meteor you see by recording it on your mobile ‘phone and transcribing it later, but make sure it is fully charged before you start.

Watches should ideally be of an hour’s duration or longer (in multiples of 30 minutes) because this will tend to even out the varying intervals between individual meteors.  You might see no meteors at all for 10 minutes and then see three in the space of a minute!  Perseids will all appear to originate from the radiant (if you extend their paths backwards) no matter where in the sky you see them. However, some of the meteors you see won’t be Perseids. Several other lesser meteor showers are active at the same time and there are also random ‘sporadic’ meteors, so if you can separate these out from the Perseids that will increase the value of your observations.

The BAA’s visual meteor report forms, available as downloads in both pdf and Excel formats, enable more experienced observers to record the details of each meteor seen. These include: time of appearance (UT); apparent magnitude (brightness); type (shower member, or random, ‘background’ sporadic); constellation in which seen; presence and duration of any persistent train. Other notes may mention flaring or fragmentation in flight, or marked colour.

When checking to see if a meteor aligns with the Perseid radiant or not, observers should bear in mind the nightly eastwards ‘drift’ of the Perseid radiant due to Earth’s orbital motion. In early August, the radiant is 15 degrees west of its position at maximum (given above), to the north of Andromeda.  It is also important to note the faintest star you can easily see (the so-called stellar limiting magnitude) and whether there are any clouds or natural obstacles which reduce the area of clear sky you can observe.

Meteor observing can be carried out by individuals, or by groups of observers working together. The element of teamwork makes meteor observing particularly attractive to local astronomical societies and the Meteor Section of the British Astronomical Association (BAA) welcomes reports from such groups as well as individual observers.

An opportunity for radio observers this year

Ionised meteor trails can reflect and scatter radio waves and many observers are now detecting meteors by this means, which has the advantage of enabling observation to be made during daylight hours and when it is cloudy!  Amateur astronomers typically use the forward scatter method to detect meteor trails. This is where the transmitter and receiver are at separate, usually well-separated locations. The transmitted radio waves are then scattered forward to the receiver from an ionised meteor trail in the atmosphere somewhere between the two locations.

Although simple forward scatter systems cannot differentiate between sporadic meteors and members of different showers, the ‘heat-maps’ produced give a very good idea of overall meteor activity levels and can pick up sudden enhancements or brief outbursts in meteor activity, that might otherwise go undetected. It is now possible to buy relatively cheap USB-based radio receivers and appropriate software to detect meteors and with some fairly basic computer and DIY skills a suitable set-up can be produced.  Anyone interested in taking up this work should contact the Radio Astronomy Group (RAG) of the BAA.

With the bright moonlight making observing conditions tricky for visual and video observers, there is a great opportunity for radio observers to monitor Perseid activity this year

Enjoy the Perseids this year

Observations in recent years have revealed noticeable variations in Perseid activity from year to year and we shall just have to wait and see what is in store for us in 2025. Meteor observing should be viewed, first and foremost, as a source of enjoyment for the observer(s). Whatever the approach and specific techniques applied, meteor observing can still produce unexpected results, and the only way to make sure you don’t miss out is to go out and observe!

To get the best view you must try to find a convenient viewing site, preferably with an unobstructed horizon, away from city lights – although the bright moonlight will spoil the show to some extent this year.  Then you must hope that the weather behaves!  Clouds could completely ruin the show.  Do wrap up warm because it can get quite chilly late on August nights.

By whatever means you observe the Perseids this year, please submit your results to the BAA Meteor Section via meteor@britastro.org.  Good luck!

Dr John Mason

Director, BAA Meteor Section

email: docjohn@dircon.co.uk

2025 August 1