Charles Messier observed this group of galaxies in 1773, while observing a comet; he described the Whirlpool Galaxy as a rather faint starless double nebula with a bright centre. First William Herschel and then his son John observed these galaxies, noting that in the central part around the nucleus there was a strange optical effect, similar to a ring surrounding the bright centre. Admiral Smith compared the primary to the planet Saturn, stating that it would have a similar shape if observed from a vertical position. Lord Rosse finally recognised very clearly the spiral structure of the primary galaxy and the obvious connection with the minor object to the north.
This is my second attempt on M51, and still Im not really happy, I collimated as best as i could, but there is still something which is not 100% correct let see in the next Galaxy season.
For now Ill let you see what I took in two night, I didn't used Dark, Flat for the PP in PI, I ll try lter to do it with them as see if it improve, not sure.
So to take this picture I used a 6" RC from TS-Optics at 1370mm FL, my ZWO ASI 533 Camera, on my EQ6-R Pro mount.
I took 200 ea. 60" Lights Frame the first Night, before the clouds came in view , and 50 ea. 180" the second night before the cloud came in..
Gain of the 533 is 101 and 70 off set.
I still have a lot to learn in general, but more on the collimation of this 6" RC, and at the same time the focusing was also a trick issue, I use an ZWO EAF connected together with the other equipment using N.I.N.A, I had several issue to get decent focus, I should re-check all the parameter, and loosing good valuable imaging time on that...but at the end is worth...