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Object data: M51, the 'Whirlpool Galaxy' in Canes Venatici is famous for its beautiful spiral structure, first noted by Lord Rosse in 1845. It was discovered by Messier in October 1773 and catalogued by him in January 1774. Its companion galaxy, NGC 5195, (seen below M51 in this image) was discovered in 1781 by Messier's colleague, P. Mechain. The M51 system is a spectacular example of interacting galaxies - in this case NGC 5195 is being "ripped apart" by the huge gravitational disturbance of M51, while M51 has in turn undergone huge structural alteration from the gravitational effects of NGC 5195. The distance of M51 is estimated to be about 37 million light years. The diameter is approximately 100,000 light years and the total mass is estmated to be the equivalent of 160 billion suns.
Please see the new image of M51 here.Date: 07/04/03
Location: Wiltshire, England
Conditions: Excellent for the UK: calm, no dew, transparency=9, seeing=8
Optics: Ritchey-Chretien 12.5" f/9 (from RCOS)
Mount: AP 900 GTO on Portable Pier
Camera: SBIG ST-8E / CFW-8
Guiding: Integral ST-8E autoguider
Exposure: LRGB: Luminance: 9x15 minutes; RGB: 15:15:30 minutes binned 2x2Processing: Image acquisition and initial processing was done using Maxim DL and AIP4WIN, subsequent processing was done using Registar and Photoshop.
Notes: This image replaces my earlier one taken in March 2001 from southern France - one of my first CCD images. FWHM was recorded as 2.2 arc seconds but I believe actual seeing was better - possibly as good as 1.8 arc seconds. A slightly binding Dec axis degraded the image slightly by causing a slight shift in RA every time the Dec axis was reversed.
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