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Object data: M104 (NGC 4594) is a bright (magnitude 8) galaxy located in the extreme south of Virgo that takes the name Sombrero from its resemblance to the broad brimmed Mexican hat. M104 was discovered by P. Mechain in May 1781, too late to be included in Messier's original catalog, but Messier added it by hand to his personal copy in May 1781. Flammarion later added it to the official Messier list. M104 is one of the brightest and most massive of the galaxies in the Virgo group. Its distance is estimated to be about 50 million light years, its diameter approximately 100,000 light years, and its total mass about the equivalent of 1.3 trillion suns!
Date of exposures: 19/2/09 & 27/02/09
Location: Southern France
Conditions: Calm, Transparency=8, Seeing=5
Optics: RCOS 12.5" Ritchey-Chretien with custom field flattener working at f/9.5
Mount: AP 900 GTO on Portable Pier
Camera: SBIG STL-11K, SBIG LRGBC filter set, -30°C
Guiding: Integral STL-11K autoguider
Exposure: LRGB Seq: 21x 15 minutes; 4x 15: 9.75 : 15 minutes (binned 2x2).
Processing: Image acquisition and initial processing using Maxim DL, subsequent processing in RegiStar and Photoshop.
Notes: This is a difficult object (even from southern France) because of the low elevation. This was compounded by poor seeing throughout the February trip, nonetheless the result is a marked improvement on my only previous image on film taken as long ago as 1998. Exposure subs were too short - should have been 25 minutes optimally.
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