Melotte 15 first NHO

[DaveS]

I'm not entirely happy with this, too messy and gaudy, but I'll post anyway as it will give a starting point for comparison later. This is "pure" NHO with no channel blending.

16 x 10 sec subs Hydrogen, 20 x 10 sec subs Nitrogen, 24 x 10 sec subs Oxygen through 3nm Astrodons. 130mm f/7 TS apo triplet, SX Trius 694 Encoder guided on ASA DDM60.

Each set of subs was stackd Sigma Average, then RGB combination followed by cropping off the alignment edges and giving Adaptive Subtract gradient removal. DDP then a single round of linear Histogram Stretch. No noise reduction yet, but a slight colour correction to reduce the magenta cast in the shadow areas.

 

Edit: Thanks to Laurin Dave, the subs are 10 Minute, NOT 10 Second. Dur....

Edited December 5, 2019 by DaveS

[JamesF]

Nice to see a result, Dave.  I know you've been collecting data for this for quite some time.

James

[DaveS]

Thanks James. It needs a lot more work, and I have some ideas as to how to proceed. I think I will try some first pass gradient reduction before RGB synthesis using just linear and vignetting, as the alignment edges mess up the fancy adaptive methods, and I need to keep the individual stacks uncropped before RGB.

May try some channel blending as well, though that means the image is no longer a pure NB that can be decomposed for scientific analysis.

[Laurin Dave]

Nice one...  especially for only ten minutes total (or did you mean minutes not secs for your subs ) I'd be really interested to know what the standalone Nitrogen image looks like, could you post it?  

Thanks

Dave

[DaveS]

Dur... yes, 10 min subs. Teach me to post in a hurry, lol

@Laurin Dave, here's a rough stack I did earlier. The FITS on my computer is still unstretched.

The [NII] does tend to reflect the HII, and even with 3nm filters there is still about 15% overlap. When I get another good clear night I'll try for some [SII] data for comparison.

[Laurin Dave]

Thanks Dave... interesting..  

[alan potts]

I don't have this catalogue so can't see where it is, it looks fine to me though when all the members do this NB lark, i never know what colour things are meant to be, to me it don't matter, the stars are rouns and it looks like a difficult subject to start with. I thing you've done a grand job on it.

Alan

[Laurin Dave]

6 minutes ago, alan potts said:

I don't have this catalogue so can't see where it is, it looks fine to me though when all the members do this NB lark, i never know what colour things are meant to be, to me it don't matter, the stars are rouns and it looks like a difficult subject to start with. I thing you've done a grand job on it.

Alan

Its the Heart of the Heart Nebula in Cassiopeia Alan...  

[DaveS]

Melotte 15 is the cluster of very massive, very hot stars in the centre of The Heart nebula in Cassiopeia that's making the whole nebula fluoresce

[geoflewis]

It looks pretty good to me Dave, though not the colour palette I’m used to seeing with NB on this target, but then I’m not a NB imager, so what do I know.... 🙄

I still need to process the HaLRGB data that I’ve collected on Mel 15, though I’m also interested to see how the new 12x15m Ha stack compares with my previous 19x5m stack, so I’ll probably start with that.

Cheers, Geof

[DaveS]

I've had another go. No DDP this time, just histogram stretch. Did a Linear and Vignetting gradient removal on the Hydrogen and Nitrogen stacks (The Oxygen gave banding), and an Adaptive Subtract on the RGB stack after cropping, then three (Or was it four lol) rounds of Histogram Stretch with one of them curves. Slight colour balance and another Linear Stretch, to give the moody, mysterious look I was after.

[Adam J]

I would be interested in seeing the individual channels as I have not seen many NII images and its hard to see where the NII is split spatially from the HA given only the combined image. 

Adam 

[DaveS]

OK, @Adam J Three stacks given linear stretching only, left uncropped. I have tried to get each to about the same levels but as I was doing by eye cannot guarantee.

First Hydrogen

Next Nitrogen]

Lastly Oxygen

You cannot say "This is all Hydrogen" or "This is all Nitrogen" unlike with Oxygen, it's more a matter of proportion.

[DaveS]

Now for a comparison. Two versions, the first is the Blue and Gold that I posted above, the second is a Green and Gold version using a different set of Input and Output mappings in the RGB synthesis.

   

Thoughts? Probably neither is "right" but what is the most likely reference / starting point for further work?

[Adam J]

Nice OIII data and I like the image in general but I guess I do wonder if there is much separation between Ha and NII in terms of where the signal is placed. I always imagined that the NII filter would perform at its best against a SN remnant / planetary nebula. In those targets you get very well defined separation between filters, more so that diffuse nebula. 

[DaveS]

Sure, but I had the [NII] filter in the wheel from an abortive attempt on M27, so thought it would be interesting to see what came up here. The [NII] signal is a lot stronger than the [SII] but now I have my [NII] data I will swap filters and go for some [SII]. I also had good results from the Rosette nebula in NHO.

[DaveS]

Looking again, I think I prefer the colour rendition of the left-hand version, but think the right hand is closer to a classic HST palette.

[bob-c]

Hi Dave,   lovely images. The blue and gold does it for me..

Bob.

[DaveS]

Thanks Bob, yes I'm coming to like the blue and gold rendition myself. that might be a good starting point for further work.