IC4628 in Scorpius

[Martin Pugh]

Hello everyone.
I am hoping that the consistently crisp, frosty and clear skies that I have come to enjoy here in Canberra will materialise soon. I also anticipate that the Jetstream will move on as it has certainly brought poor seeing also.
Indeed, I threw away all 12 frames from 2 nights ago as they were all over 3".

However, there have been sufficient clear nights for me to acquire 23
hours NB exposure on this lovely nebula in Scorpius, fondly known of
course as the Prawn Nebula.

I shot this some time ago with an FS128/STL11K, also in NB, and it
was a very pleasing result, and secured an APOD. I had to come back to it with the RC and will return to it again to add a second panel for what will be a 2-frame mosaic.

STL11K, AOL, Astrodon NB filters mapped as SII (Red), HA (Green), and
OIII (Blue)

thanks for looking and comments/critique welcome of course.

cheers
Martin

http://www.martinpughastrophotography.id.a u/images/IC4628NB60pct.jpg

[leon]

Martin, all I can say is that is awesome, 23 hours you say, now that is what I call imaging, fantastic work.

leon

[gregbradley]

That is an amazing image Martin. So clear and sharp and so much depth.

Greg.

[Martin Pugh]

Thanks Leon/Greg.

I appreciate your comments.

cheers
Martin

[jase (Jason)]

Nothing short of remarkable Martin. Very well done. I'm intrigued by your narrowband processing technique. This image and the dark tower displays interesting "muddy" hues which to be honest is not what I'd expect from a SHO palette. I would have expected a much greater presence of green considering the Ha presence in the target. Are you using clipping masks to manage the palette?

[renormalised (Carl)]

Great work there, Martin

The detail in the nebula is stunning

It would be interesting to compare this shot to a LRGB piccie of the same area at the same resolution.

[jase (Jason)]

Sure this wasn't taken with the 12.5" RC. Diffraction spikes kind of give it away.

[Martin Pugh]

Thanks chaps.
Maybe my wording of the post was mis-leading...this image is taken with a 12.5" RC.....my previous image of this object, both NB and RGB were taken with the FS128/STL11K.
The page is here:
http://www.martinpughastrophotograph...lae/IC4628.htm

Jase...as you well know, the 'correct' balancing for the SHO palette is a totally green image. I use the same HA component, completely unprocessed as both 'Green' and Lum. I purposefully adjust the SII and OII to reveal the lovely reds, yellows and blues.
I have developed a technique which almost, not completely, eliminates the heavy magenta stars that occur when you combine these frames in this way...its very effective. Any bright stars that remain with a magenta halo are then gently desaturated with the sponge tool and then the area made more natural with a combination of the dodge/burn tools.

I dont use clipping masks to manage the pallette...I simply use weightings to get the result I want, then I use pixel math to apply the weightings....when you display the 3 images alongside one another after this, their respective brightness levels are roughly equal.

glad you liked it

cheers
Martin

[jase (Jason)]

Hi Martin,
I've tried a similar process before when processing NB images. Using MaximDL colour combine function to determine what "looked" right (as there technically is no wrong). Start with a 4:1:3 ratio for SII:Ha:OIII respectively and turn on background equalisation before making final adjustments. Once they look right, take note of the adjustments (ratios). Then using pixel math to subtract the background on each combined sub, but making sure you leave the pedestal. This ensures the subs are all equalised, then use pixel math again to scale the images based on the ratios previously noted i.e 4.2 would be 420%. Once the individual subs scaled, go back into the colour combine tool and combine with 1:1:1 ratios. I think this is what Russ Croman explained at the 2005 AIC. I've had mixed results using this method and find clipping masks give greater flexibility. This has been in my limited NB processing experience anyway. You could always re-layer the stars to circumvent the NB halo phenomenon. Again and lovely image. Well done.

[Ric]

Hi Martin, what a stunning image. The narrowband filters show up the nebulosity wonderfully as well as bringing some fantastic colours hues.

An excelent image and I really looking forward to the second panel.

cheers

[Martin Pugh]

Thanks Ric, I appreciate it.

'Renormalised' .....you ask and I shall give!

Here is the same image, utilising the same data, but processed as LRGB

I hope you like it.

cheers
Martin
http://www.martinpughastrophotograph.../IC4628RGB.jpg

[renormalised (Carl)]

Just as good, Martin

The amount of detail is very impressive.

[skeltz (Rob)]

Love it martin...hmm seem to have seen this on another siteand as i said before i cannot wait to see the final result cheers/