M100 - Coma Berenices

Object data: M100 (NGC 4321) is one of the brightest (magnitude 9.3) members of the Virgo group of galaxies. It is located to the north of Virgo in Coma Berenices, but still very much part of the Virgo group. It has many young, high temperature giant stars in the spiral arms giving them a predominantly blue colour. The shape has been heavily influenced by companion galaxies, three of which are visible in this image. M100 was discovered by P. Mechain in 1781 and catalogued by Messier in April that year. It is estimated to be 60 million light years distant with a diameter of about 160,000 light years, and with a total mass of about 160 billion suns. Date: 26/03/01 Location: Southern France Conditions: Calm, transparency=7, seeing=6 Optics: Ritchey-Chretien 12.5" f/9 (from RCOS) Mount: AP 900 GTO on Portable Pier Camera: SBIG ST-8E / CFW-8 Guiding: ST-4 via custom OAG (designed by Chuck Vaughn) Exposure: LRGB: Luminance: 8x10 minutes; RGB: 10:10:20 minutes binned 2x2 Processing: Image acquisition and initial processing was done using Maxim DL, subsequent processing was done using Registar and Photoshop. Notes: This image is from a batch of first light images using the new RCOS 12.5" and the new ST-8E. It is also one of my first CCD images. A known problem with this image is that the indivual luminance exposures were not deep enough. There was also a major problem with large gradients in each of the RGB exposures. These gradients have been seen in all RGBs so far taken, despite great care with flat frames, calibration etc. In some cases the gradients can be removed with the "Flatten Background" function in MaximDL, but not in this case. This image was cropped slightly from the original 1530x1020 chip resolution and in addition downscaled slightly for optimum monitor resolution.