M51 The Whirlpool Galaxy in the Canes Venatici , estimated to be 23 million light-years distant. The spiral structure is believed to be the result of the close interaction between it and its companion galaxy NGC5195
The red knots visible in the spiral arms are star birth or HII regions.

Taken the nights of June 10 and 11, 2016 from Highland Lakes, New Jersey

Celestron C8 with Starizona reducer/corrector @f7.5 (1500mm EFL)
Celestron CGE mount, guided off-axis, Starlight Xpress lodestar with PHD Guiding
QSI 583wsg with Baader filters

L(Ha) R(Ha)GB
Luminance 30 x 5 minutes
RGB 10 x 4 minutes each
H-alpha 36 x 10 minutes each

All subs binned 2x2

Acquired in Astroart, PHD Guiding for guiding. Stacked, flats and darks applied in Deep Sky Stacker.
Processed in Adobe Photoshop