A galatic sunflower

[Hughsie]

A galactic sunflower.

 

My rendition of Messier 63, the Sunflower Galaxy located in the constellation of Canes Venatici.

 

Lord Rosse identified the spiral structure to the galaxy, one of the first galaxies in which this structure was identified. It is considered a flocculent spiral as it does not have clearly defined arms but infra-red analysis shows that it is made up of two spiral arms dotted with regions of star formation and dust lanes. If you zoom into the galaxy you will see the dark dust lanes described above along with the red/pink areas within the spiral arms that highlight areas where stars are being born.

 

This image was taken across three nights, 10th, 11th and 15th April with imaging taking place each night from 22.00 to 04.00 the following day. 

 

- Image 1 - LRGB cropped.

- Image 2 - LRGB wide field.

- Image 3 - Plate solved field of view revealing other galaxies listed in the Principal Galaxies Catalogue.

- Image 4 - LHaRGB wide field (too pink for me).

 

Equipment

To capture the galaxy I used a William Optics Z103 refractor. This has an aperture of 103mm and focal length of 710mm but when combined with the 0.8x reducer/flattener the focal length reduces to 568mm. As a result I feel the above equipment gave too much of a wide field view whereas a larger aperture/focal length would have produced a larger image.

 

For those of you interested in the process of taking the individual images and turning them into a single picture then please read on.

 

Image Acquisition through Sequence Generator Pro 

Across each session I captured the following individual frames using a ZWO ASI1600mm Pro Cooled mono camera and an ZWO electronic filter wheel. The camera was set at a gain of 139 and offset of 21 then cooled down to -20 degrees centigrade to help reduce noise;

 

Luminance 44 x 3 mins

Hydrogen Alpha 52 x 5 mins

Red 16 x 5 mins

Green 17 x 5 mins

Blue 17 x 5 mins

 

Overall the final image represents 10.7 hours of exposure time but actually far more time was dedicated to this but I decided to bin the data I captured on 4 April 2020.

 

All images were unbinned using 1.25” Chroma LRGB and Chroma Ha 3nm filters were used. It could well do with more colour. 

In addition, the following calibration frames were taken;

Flats for each filter x 50

Dark Flats x 50

Dark frames (50) to match the Gain/Offset/Camera temperature and exposure (I have created a dedicated Dark library to so that I don’t have to take them after each imaging run).

 

PixInsight processing 

The following processes were then applied to each individual filter set post calibration;

-Each image cropped to remove edges and dark bands created after stacking.

-Dynamic Background Extraction applied to remove remaining gradients and light pollution effects.

- Deconvolution applied to the Luminance master to improve resolution.

- Established which of the RGB masters is brightest and applied Linear Fit process to the R and B masters using G as a reference.

- Colour Combination with R, G and B masters to produce a colour image.

- Applied Photometric Colour Calibration to balance RGB channels and provide a neutral background.

- Noise reduction applied to Luminance, Hydrogen Alpha and RGB masters.

- Luminance, Hydrogen Alpha and RGB masters stretched to produce a permanent image.

- Luminance master combined with RGB using LRGB Combination to bring in the detail to the RGB master.

- Further noise reduction applied to LRGB master.

- Hydrogen Alpha master combined using 50% Ha and 50% LRGB using the NBRGBCombination process.

- Enhanced colour of stars using Curves/Colour Saturation with a range mask to protect the galaxy. This was then inverted to protect the background so that the colour of the galaxy could be enhanced.

- Enhanced contrast to bring out the dust lanes in the galaxy using Dark Structure Enhance process.

- Sharpening using Unsharp Mask.

- Minor adjustments to curves and colour to adjust brightness and saturation levels.

- Then a cup of well earned tea some 5 hours later (not including the calibration process)!

 

I hope you have enjoyed the ’story’ and the Sunflower Galaxy.

 

John

 

 

 

[geeklee]

Lovely image John, loads going on in the wide field too.  Did the Ha provide the extra red/magenta detail boost in the galaxy or did you have a lot of it already with RGB?

Thanks for the PI processing workflow info as well.

[Hughsie]

Hi Lee,

The Ha turned the image a pinkish colour which looked unnatural to me but it did reveal the star forming areas. The bottom image contains Ha. If you zoom in you can see the pinkish blobs. The red didn’t reveal much. In the end I couldn’t decide between LHaRGB or LRGB. Mrs H preferred the latter and having looked at it again this morning I think she was right but......sssshhhhh....dont tell her that

Thank you for your comments and I am glad the PI workflow was useful too.

John

[geeklee]

3 minutes ago, Hughsie said:

Hi Lee,

The Ha turned the image a pinkish colour which looked unnatural to me but it did reveal the star forming areas. The bottom image contains Ha. If you zoom in you can see the pinkish blobs. The red didn’t reveal much. In the end I couldn’t decide between LHaRGB or LRGB. Mrs H preferred the latter and having looked at it again this morning I think she was right but......sssshhhhh....dont tell her that

Thank you for your comments and I am glad the PI workflow was useful too.

John

Ah, sorry, the text is white on white in my view of the forum (no black background) so I need to highlight it to read it.  I was scrolling up and down and viewing the initial images in 1:1 in their own tab so somehow missed the last one. I agree on the LRGB 👍 Not sure if you could blend in the Ha to a masked area based on the colour mask script in PixInsight (so boosting galaxy areas of magenta/red perhaps)?

[Hughsie]

15 minutes ago, geeklee said:

Ah, sorry, the text is white on white in my view of the forum (no black background) so I need to highlight it to read it.  I was scrolling up and down and viewing the initial images in 1:1 in their own tab so somehow missed the last one. I agree on the LRGB 👍 Not sure if you could blend in the Ha to a masked area based on the colour mask script in PixInsight (so boosting galaxy areas of magenta/red perhaps)?

Worth a try. Will take a look at the weekend.

[MarkAR]

Lovely image and a great write up.

[souls33k3r]

That's a mighty fine image John. 

I always wondered how do you guys manage the 3 - 5min exposure using broadband filters? I couldn't even get past the 60s mark without blowing my mean readout off the roof. 

With my SCT, I try to stay between 900 - 1500.