M51

[JohnH]

A fairly wide field image of M51



Approximately 7 hours 30 mins of imaging.

Luminance HaO + R + G + B
Chrominance Ha + R + G + B

Sharpstar 15028 HNT 150mm f2.8
ZWO ASI1600MM Pro

[Carole]

With the geneuine tidal tails, and without the miscreant tidal tails.  Well done for you peseverence.  Nice image.  I'd be in clined to do a separate Crop as well. 

Can you explain what Chrominance is compared to Luminance and why you need both? 

[JohnH]

Thanks Carole,

My working theory is that simply using a Dual Band filter for Luminance would mean that some areas with detail might be completely missing because there would only be data from the narrow Ha and OIII bands. That is why I have added an arbitrary 25% of my RGB data.

For chrominance I use RGB data and a "Photometric Continuum" subtracted Ha layer. Again, my working theory is that Blue/Green data will be picked out by the OIII Luminance and the Ha/Red data will be picked out by the Ha Luminance.

For both layers I use a Masked Stretch followed by a Generalised Hyperbolic Stretch to pull as much detail as possible. I the use the Pixinsight Multiscale Linear Transform process to further sharpen the Luminance layer.

Starexterminator then gives me the subject layer and star only layer which I process separately in Affinity Photo 2 before recombining.

Obviously, some or most of this may be wrong or unnecessary  but I think that my images are considerably improved.

[JohnH]

I have further cropped the image. I wanted to keep the small galaxy on the left.

(Edit) I have de-noised the tails.

[The Thing]

Very. Very. Nice.

Lovely detail and colours,