NGC 6559 Chinese Dragon Nebula in HOO

[Startrek]

The nights have been cloudy for 2 weeks since returning from a trip so decided to reprocess NGC 6559 which was captured back in September and posted as an SHO version.
This time I processed a Bi colour HOO version which ended up having a higher noise floor to work with due to my noisy Oiii data. Capturing Oiii data under B8 skies and a moon around is not pretty , faint signal and lots of noise.
Anyway pushed the detail as far as I wanted to whilst balancing the fine noise grain.
Happy with the detail and contrast through the central core region

Same deal ……
B8 skies
Conditions poor to average ( some high cloud around )
Moon around
8”f5 Carbon Newt
EQ6-R pro mount
ZWO 2600MM with Antlia 3nm filters
3 minute dithered subs Gain 100 , -10C
12 hours of integration
Flats , Darks , Flat Darks
EQMOD , Stellarium, APT, PHD2
ASTAP
Startools V1.8 via Compose , Colour HOO preset with tweaks

Astrobin link for full resolution……..,

https://www.astrobin.com/xcjogs/

Thanks for looking

Comments welcome

Martin

[dx_ron]

Very nice! It looks 'soft' - not like out of focus, just like a fluffier nebula than I'm used to. I looked at a few other abin images and they looked that way to me, too. I like the shade of blue you coaxed out of it for the O, something I always struggle mightily with my OSC+duoband filter.

[Startrek]

Thanks
This nebula is basically an extension of M8 Lagoon which is vastly different.
It definitely has fine “fluffy” nebulosity and lacks those distinct ridged structures that most nebula exhibit but its unique.
I struggled as well with my OSC and dualband to replicate those stereotypical Hubble palette colours , in particular the golden tan hues and light blue hues. I guess Startools has its limits in the Colour module using OSC dualband data as the Oiii is so damn weak. However, folk on our local forum can produce some excellent OSC narrowband images in Hubble palette using , you guessed it Pixinsight.

That’s one of many reasons I jumped into Mono and dedicated narrowband filters after 4 years with OSC.
Startools Compose and Colour Module has allowed me to process my Mono data sets and create bonafide Hubble palette images in SHO, OHS , HOO and so on…… with those beautiful golden tan hues , Cyan , tomato reds and light blue hues.

My OSC is rarely used now but when I do it’s generally for a 1 night capture of broadband targets like galaxies and globular clusters etc…

Cheers
Martin

[jlh]

Hi Martin,

Do you Wipe your OSC Ha and OIII channels separately before loading them in Compose? I find that doing that separately, along with applying the same needed Bin and Crop, improves the availability of the OIII signal for post-Wipe processing in StarTools. When you get to Color the popup thinks Wipe has not been used but I haven't seen that as a problem. Maybe it is just my imagination but it seems that using Wipe on the combined HOO image reduces the available OIII data vis-a-vis the Ha.

Jeff

[Startrek]

Hi Jeff,
Interesting observation about your Oiii signal
I’ve never split my OSC Dualband ( Ha / Oiii ) data set for narrowband Bi colour renditions, I’ve always just loaded my OSC Dualband data set into Compose via R/Sii, G/Ha and B/Oiii and selected the Luminance , Colour as L + Synthetic L from R(2xG)B, R(GB)(GB) (BiColor from OSC/DSLR) - Creates synthetic luminance data from the R,2xG and B channels combined, and the colour from the R and G+B and G+B channels (Standard HOO palette)

I think splitting OSC narrowband data sets into Ha and Oiii channels was required prior to ST 1.7 where Luminance , Colour options didn’t include OSC Bi colour etc…,

I suppose I could experiment a bit and split the OSC data set via Compose into separate Ha and Oiii tiff files.
What Luminance , Colour selection should I use to do this ??

Then I assume you would open Compose , load Ha into R/ Sii slot , Oiii into G/Ha slot and Oiii into B/ Oiii slot.
Luminance, Colour could probably be L + Synthetic L from RGB, R(GB)(GB) (BiColor) - Creates synthetic luminance data from the R,G and B channels combined, and the colour from the R and either G or B channels. Useful for creating Bi-colour images from 2 narrowband filtered datasets ??

When using my Mono camera with a dedicated 3nm Oiii filter the Oiii signal is substantially weaker than Ha more so with certain emission nebula where it’s extremely weak. At least Mono has the flexibility of capturing more Oiii than Ha for these emission nebula that emit super weak Oiii signal , OSC unfortunately doesn’t have that luxury.

Clear Skies
Martin

[jlh]

Hi Martin,

I use APP for stacking and it has an algorithm for splitting out Ha and OIII from OSC duo band captures. You can process those mono Ha and OIII mono files like mono captured Ha and OIII files in StarTools. As I mentioned above, I first load and Wipe each mono Ha and OIII file separately. I then reload those Wiped files in Compose with the usual HOO parameters and start with the second global stretch, skipping Crop, Bin, and Wipe. Again, I don't know if this creates problems in StarTools but it seems to help with the OIII coloring.

Jeff

[Startrek]

Jeff,
Yes a lot of folk on our local forum use APP for their OSC data , very intuitive
I assume before your first Wipe , you Crop edges ( same cropped image size for both Ha and Oiii ) for stacking artefacts etc… and Bin ( same Bin for Ha and Oiii ) to maximise your SNR ?

I don’t think Compose has any issue with Data which is Wiped.As long as it aligned and sees the same image size in all channels before it attempts to Compose the data.

Martin

[jlh]

Hi Martin,

I assume before your first Wipe , you Crop edges ( same cropped image size for both Ha and Oiii ) for stacking artefacts etc… and Bin ( same Bin for Ha and Oiii ) to maximise your SNR ?

Yes. StarTools is very good in that it remembers the exact Crop settings from one image to the next as long as it is not closed.

Jeff