Messier 51 (NGC 5194), the Whirlpool Galaxy, is a face-on spiral galaxy located approximately 23 million light-yeas away in the constellation Canes Venatici and is one of the most well-known galaxies in the night sky. This galaxy has an apparent magnitude of 8.4 and has a radius of approximately 43,000 light-years. Its mass is estimated to be 160 billion times that of our Sun. M51 was discovered by Charles Messier on October 13, 1773 and its companion galaxy, NGC 5195, was discovered in 1781 by Pierre Mechain. Telescope: Celestron 8” EdgeHD @ f/10 Accessories: Dew control by Dew Buster Mount: Takahashi EM-200 Temma2 Camera: QSI583wsg CCD @ -10.0C Guiding: Starlight Xpress Lodestar via PHD Filters: Astrodon Tru-balance E-Series Generation II LRGB; Astrodon 5nm Ha Exposure: 41 x 6min.(L); 9 x 20min.(Ha); 10 x 6min.(R); 10 x 6min.(G); 10 x 6min.(B); all frames binned 2x2 Acquisition: ImagesPlus Camera Control v4.3 Processing: Calibration, DDP in ImagesPlus 4.5b; Registration in RegiStar Post-processing: ImagesPlus 4.5b; Adobe Photoshop CS5; Gradient Xterminator, Noise Ninja Date(s): April 1, 2, 6 & 9, 2012 SQM reading (begin - end): N1:18.63 - 19.11; N2:17.38 - clouds; N3:?; N4:? Temperature (begin - end): N1:70.7ºF - 63.7ºF; N2:74.7ºF - 67.1ºF; N3:54.9ºF - 42.8ºF; N4:67.0ºF - 55.0ºF Capture conditions: N1 - transparency: Avg 3/5; seeing: Avg 3/5; N2 - transparency: Avg 3/5; seeing: Good 4/5; N3 - transparency: Above avg 4/5; seeing: Avg 3/5; N4 - transparency: Avg 3/5; seeing: Avg 3/5 Location: Hendersonville, TN, USA