Located approximately 55 million light-years away, in the southern part of the constellation Coma Berenices, is Messier 100, a nice example of a grand design spiral galaxy. A member of the Virgo cluster, M100 is one of the largest and brightest of the group, with a diameter of 107,000 light-years. It was discovered by Pierre Mechain on March 15, 1781 and added to Charles Messier's catalogue of nebula and star clusters after his observation of it on April 13, 1781. One of the first spiral galaxies to be discovered, M100 was listed as 1 of 4 spiral nebulae by Lord William Parsons of Rosse in 1850.
There are two satellite galaxies associated with M100 – NGC 4323, connected by a bridge of luminous matter (around the 8 o'clock position right next to the galaxy in this image), and NGC 4328 (at the 6 o'clock position in this image).
Other designations: NGC 4321
Telescope: Celestron 8" EdgeHD SCT @ f/10
Accessories: Dew control by Dew Buster; Aurora flat panel
Mount: Takahashi EM-200 Temma2
Camera: QSI583wsg CCD @ -10.0C
Guiding: Starlight Xpress Lodestar
Filters: Astrodon Tru-Balance LRGB
Exposure: 7 & 1/2 hours total: Lum (1x1) = 18 x 900sec (4 & 1/2 hours); RGB (2x2)= 6 x 600sec each (3 hours)
Acquisition: ImagesPlus Camera Control 5.0
Processing: PixInsight 1.8
Date(s): April 26, 2014; May 1 & 2, 2014
SQM reading (begin - end): N1:21.35 – hazy humidity / high clouds; N2: 21.17 - 20.76; N3: 21.24 - 21.25
Temperature (begin - end): N1: 58.8ºF – 53.8ºF; N2: 46.8 - 43.3F; N3: 49.1 - 40.5F
Capture conditions: Transparency: N1: avg 3/5; N2: avg 3/5; N3: above avg 4/5; Seeing: N1: avg 3/5; N2: avg 3/5; N3: avg 3/5
Location: N1: Spot Observatory, Nunnelly, TN, USA; N2 & N3: Fall Creek Falls State Park, Spencer/Pikeville, TN