The villages of Seavington St Mary and Seavington St Michael in South Somerset

Noctilucent Clouds

This article by Ken Osborne was published in the May 2007 Seavingtons’ News

One of my Hobbies has been, and is, an interest in Astronomy. One of the associated areas is phenomena that occur in the Earth Space boundary. The main one that occurs that is of visual interest is the Northern Lights – Aurora Borealis – I can deal with this matter another day. Since I moved to the village I have seen from the back garden some 25 Auroras – and I have taken photographs of at least 3. At the moment and for the next few years they are not likely to be any significant events so I wil,l when they start to rise again, enter an article to assist those that are interested.

The phenomenon that I wish to bring to interested people is a rare form of cloud – only visible after sunset – these are called NoctiLucent clouds (night lit) – NLC. These clouds are well above normal Clouds which generally go up to about 10 miles – these exist in a layer that is 50 to 80 miles up – a long way. They are thought to be formed from Ice crystal etc. They usually are seen between about Early May to Late August each year – and mainly at high latitudes – they are more common in Finland, Norway and Sweden and similar latitudes in the USA. They are however getting more common at UK Latitudes and are now being seen down in the south of the UK – and even as far south as the Mediterranean from time to time.

There is a belief that they are getting more prevalent due to Global warming – this may be so – but it is a fact that since the 1880s when they were first really documented their occurrence has increased – and more so in the last 10 to 15 years.

They are very easy to differentiate from normal clouds – they have a wispy, steel blue colour. They can be visible, if the display is big and strong not long after the Sun has set and the sky is starting to darken. They can show as far as 45 degrees above the horizon – normally you should look from about North to Northwest. The display should then get brighter as the sky darkens and they can, at times give the affect of the sky being still very light – so light that you can read a paper by them!!. As the Sun sinks further the display will appear to move nearer the horizon – but this is because the rays of the set sun, which is now set by at least 1 hour to 1.5 hours is illuminating less of the clouds. If you are lucky you can have a very clear cloudless sky and get a superb display – I was lucky one night last July and took many photos from the playing field over about 1.5 hours – and even then they were still visible. Some examples are at the top of this page; click any picture for an enlargement.

I suggest that if you are out and about as indicated above – look northerly and you may be lucky. Not all displays are big or bright – but may well be still obvious as the normal clouds will be backlit by the NLC so the normal clouds will look black.

If anybody wishes to contact me I am happy to pass on any further information – and if there is a display alert them to that fact – Ken Osborne (01460 241223).


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