Noctilucent clouds - 9th July 2010, 22:30GMT - 00:00GMT

[MuammarAlGathafi]

NATO is spraying you with toxic chemicals.

[george7378]

@MuammarAlGathafi I don't think a brainwashed extremist like you has the right to comment on astronomy videos.

[ThinkingManNeil]

I saw some several years ago during a summer in northern Alberta. Quite bright. Thought they were aurora at first but they didn't "move" or vary in brightness. Fascinating.

[EIN771]

those are very beautiful.... do you mind me asking how they are formed? or when is the best time to look out for them?

[george7378]

@EIN771 Hi - I agree; they are very special and mystifying to see. They are best seen when the nights are short in summer. You will have to look towards the sunset (north-west) or the sunrise (south-east) to see them because they are illuminated by the Sun at high altitudes when the ground is dark (like satellites). We don't know how they are formed, but it is certainly not due to condensing water vapour, like normal clouds. Theories include rocket exhausts, meteor dust and global warming.

[MChuter22]

I saw them last night as well...

A very nice display, lots of colour and prominence.

Perhaps some more visible tonight (10th July).