Why I love NB Mono Imaging, and a Conundrum...

[Mike Lewis]

So here are some versions of M27, also known as the Dumbbell Nebula. As the title suggests, the 2 main versions were imaged in NB, with data collected from all 3 common filters, Hα, OIII, and SII. This is a fun target as it has an OIII signal that is just as strong as the Hα signal (more common for planetary nebulae like this one), although the SII signal was fainter. This is the first narrowband target I have imaged with the EdgeHD 925 and I remain very happy with my results. As I like to do I also took 30 sec subs to allow addition of RGB stars (35 mins total) back into the image at the end of the processing.

The results are shown here in 2 different palette mixes, and it is here that I really like the flexibility I get from having totally separately captured data for each of the emission bands, allowing me to really 'play' with the final result. It could be considered to be a double edges sword by some - I spent like upwards of 10+ hours just fiddling with the mixing methods, signal ratios, and color balancing to get some versions I liked. I would estimate there was at least half that much time also spent on all the other processing steps as well, maybe more (I don't keep track of such things really). Actually longer processing time than time spent collecting the data (in this case that was 15:49, but with critical data culling I only used 11:55 of data for processing). For many that is just too time consuming, but for me, it is a great part of the fun of this hobby, working on your data and slowly seeing what can be teased out of it.

So now the conundrum: I am not quite sure which of the 2 narrowband versions I like the best, so both are presented here. I likely will only post one to the larger world once I settle on a favorite, but interested to see which is favored by our discerning folks here on FW. I also did a VERY quick and dirty (more like 15 mins instead of 15 hours ) post process of just my RGB data, to allow a quick comparison to the difference between RGB and narrowband capture on this object. It is a very unfair comparison, as the RGB data is 35 mins and the NB data is 715 mins so 20 times less integration on the RGB. I am sure there are MANY deeper and more detailed versions of M27 in RGB to be found, but beyond showing what is now achievable with even a small stack of data I primarily wanted to show the comparison of M27 in natural color to what I have created in NB, to emphasize the different looks. I hope everyone who views this enjoys the comparisons and chimes in with a preference for the 2nd and 3rd images. As always comments and critiques are most welcome.

35 minutes of RGB data (used just for the stars in the next 2 images but used here for color comparisons between RGB and NB) Easier to see the Dumbbell here I think...

M27, in a somewhat conventional modified SHO palette with Orange/Blue mix (Mix5 in my progression)

M27, with a more Magenta hued mix (Mix6 in my progression)

Collection Hardware, Software, and Details:

Equipment:
ZWO ASI1600MM-C Camera @ -10C and Gain:139 Offset:21 (LRGB)
Gain:200 Offset:50 (Hα)
Software Bisque MyT Mount
Celestron EdgeHD 9.25 SCT with 0.7x reducer, 1645mm @ f/7

Software:
PHD2 Guiding Software
NINA Astroimaging Software
Pixinsight Commercial Version 1.8
Software Bisque TheSkyX
Lightroom CC
Photoshop CC
Russell Croman BlurXterminator
Russell Croman StarXterminator
Russell Croman NoiseXterminator

Light Frames:
Ha - 20 x 600 secs ( 3 hrs 20 mins)
OIII - 20 x 600 secs ( 3 hrs 20 mins)
SII - 28 x 600 secs ( 4 hrs 40 mins)
Red: 24 x 30 secs (12 mins)
Green: 23 x 30 secs (11 mins 30 secs)
Blue: 23 x 30 secs (11 mins 30 secs)

11 hrs 55 mins total

Dark Frames:
10 x 30 secs (5 mins)
10 x 600 secs (1 hr 40 mins)

Flat Frames:
10, each filter

 

[JimFox]

Hey Mike,

What a fun and interesting display of some of the variations available when processing our Astro data.

You are correct that in shooting with a Mono Astro camera, you have the most flexibility. For those who may not have caught it, for a typical image you capture you are using 7 different filters right?

While Color Astro (OSC) cameras do not have quite the flexibility or light gathering power, I will say it's caught up quite a bit in the flexibility department. If Mono has 100% flexibility, I would say that Color is now up to 90%. Guys like Lukomatico have been doing great jobs with tutorials on how to take the Color Data and then in Pixinsight separate that data into Ha, Oiii and Sii, and then recombine them. It's not perfect or exactly the same as shooting with a mono camera, but it gets the color closer to what a mono can do.

Now....

It's nice to have that reference as to what RGB would look like. That's a view that's probably close to what a Color camera would output without any editing. What I like in that version is the cyan/teal color of the dumbell. When I have seen other images, that's the color that personally I am attracted to the most.

It's hard to chose here... as I like aspects of them all...

For me, here would be my goals if I was processing this.

1. I want to keep the dumbell looking cyan/teal.

2. I want the arms around it to look reddish.

So not sure if this is ethical, but in Photoshop, could you use the Color Selection tool to keep the Cyan/Teal of the RGB and create a mask to protect it, while overlaying the Red arms of #3?

Or.... taking #3 into Photoshop, load it into ACR and then in the Color Mix, go to the Purple color and slide it's hue slightly to the blue. I think that might also change the dumbell back towards the Cyan/teal color.

Now, all of that is based on my vision.... Yours may not be like that. So I am not sure if I totally went off the rails as to your question or not....

 

[chuckp]

Hey Mike I like the second one a little better. Have you tried HOO process I think that might even work out better. I also like the rgb one.

 

[Dan Moorehead]

Wonderful choices