This target is a bit of stretch for my rig, as it is relatively small in the FoV of my Esprit 100. The image seen here is after cropping about 50% of the total FoV to render the target large enough to be the center of interest.
This is an integration of approximately 4 hrs and 40 minutes of observing time with an dual narrow band filter (L-Extreme). The image was split into LRGB layers, the B was discarded as a primary 'noise' channel and a substitute was created from a mix of the R and G channel. The L channel was enhanced to bring out some of the dimmer structure. This would likely be a relatively simple target to process from a longer focal length OTA, but given the wide field of my OTA some care has to be taken to prevent obscuring or eliminating some of hte fine detail on the small scale.
From Wikipedia:
What later became known as the Whirlpool Galaxy was discovered on October 13, 1773, by
Charles Messier while hunting for objects that could confuse comet hunters, and was designated in
Messier's catalogue as M51. Its companion galaxy,
NGC 5195, was discovered in 1781 by
Pierre Méchain, although it was not known whether it was interacting or merely another galaxy passing at a distance. In 1845,
William Parsons, 3rd Earl of Rosse, employing a 72-inch (1.8 m)
reflecting telescope at
Birr Castle, Ireland, found that the Whirlpool possessed a
spiral structure, the first "nebula" to be known to have one.
These "
spiral nebulae" were not recognized as galaxies until
Edwin Hubble was able to observe
Cepheid variables in some of these spiral nebulae, which provided evidence that they were so far away that they must be entirely separate galaxies.
The advent of
radio astronomy and subsequent radio images of M51 unequivocally demonstrated that the Whirlpool and its companion galaxy are indeed interacting. Sometimes the designation M51 is used to refer to the pair of galaxies, in which case the individual galaxies may be referred to as M51a (NGC 5194) and M51b (NGC 5195).
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