Saturday, 3 April 2010

The Whirlpool

This fine galaxy is filled with fascinating features. The Whirlpool galaxy (M 51) is now climbing high in the sky and can be found near the tail star of the Plough, Alkaid. It is not one but two galaxies, the second (NGC 5195) has been shown by computer simulation to have passed through the main one twice. I am pleased to have revealed in this image the glowing areas of stars surrounding NGC 5195 that are the result of the aforementioned collision. To get this image I have combined the 10 least trailed shots with 19 very badly tracked ones, which I detrailed using Paint Shop's Layer/Darken function. I stacked the first 10, then all 29, and processed them both separately, applying a careful smoothing blur to the faint areas. Only by stacking all 29 shots could I clearly see the filament shooting out at the top of the image. I then cropped both to the same area and blended them in the ratio about 2:1 in favour of the sharper 10 frames. The total exposure time was just 15 minutes at f/3. I was quite taken aback when my stacking program output showed me the extremely deep areas to the left, which have incredibly subtle contrast against the sky background.
Another great thing in this picture is the exceedingly thin splinter of IC 4277, a 16.5 magnitude galaxy hiding just to the left of the main galaxies. This has one of the highest aspect ratios I've seen although it has been a little blurred in the processing. IC 4278 is also here, lying below NGC 5195.
Imaging reveals so much more than the eye will ever see directly. Even the Sixth Earl of Rosse would never have seen anything like this when he made his famous drawing of this object on his 72-inch Leviathan telescope at Birr Castle.

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