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Removing Blemishes


Nacreous clouds

This photograph (by Lee) shows a spectacular display of nacreous clouds seen over Leeds in 1995 [actually 1996 -- see below], showing strong irisation. The event was unusual enough to appear on the news broadcasts of the day. Note well: the colours are real - no enhancement has been done. This is a scan from an original print, taken with a Minolta camera.

It's a pity about the telephone wires, though...

This was my first attempt at large-scale retouching, and it turned out to be quite educational. I used the Cloning effect to remove the wires, but the nature of the image, with large areas of subtly changing colours, posed various problems. I had to be very careful in choosing the areas to copy from, especially on the cloud borders. It was important to get the brush size and opacity right, and the manner of application made a difference too (don't "wipe" with the brush - "dab" with single mouse clicks). The end result has visible flaws, and one day I'll try again.


Wireless clouds


If you want to learn more about nacreous clouds and other natural displays, get hold of the extraordinary book Color and Light in Nature by David K. Lynch and William Livingstone (second edition; Cambridge University Press 2001, £19.95).

Addendum (18 Aug 2002)

Further research has pinned down the exact date and nature of this event. It occurred on 16 February 1996, and was indeed an example of very rare nacreous clouds as we had deduced (not noctilucent clouds, as sometimes reported). It was seen over various parts of the UK. There was a discussion on the subject in the sci.astro.amateur newsgroup entitled "WIERD [sic] CLOUDS OVER LEEDS (UK)", with one particularly interesting and knowledgeable contribution coming from Alan Pickup of the Royal Scottish Observatory (and currently the writer of the Guardian's regular 'Skywatch' astronomy column). It's the 11th message in the thread, and here's an extract:

However, the clouds seen widely on February 16 were _not_ noctilucent clouds. Rather, they were the very much rarer nacreous clouds, also called Mother of Pearl clouds. These, too, are ice crystal clouds, but at about 25 km altitude where they hang like vast chandeliers refracting sunlight in a rainbow of colours. Having seen both types, I can say that nacreous clouds I saw were much brighter and more colourful than noctilucent clouds. [...]
Perhaps "Chandeliers in the Sky" would have made a better title for Lee's picture....

More pictures of this particular event can be seen at the following sites:

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