First attempt at Narrowband, comments tips & suggestions?

[Notty]

As I have found myself with a the time to get the new kit cobbled together and finally all the software and gubbins all updated and speaking to each other, I could not wait to shoot my first test shots with my new camera and filter wheel, filters etc.  Could not wait to have a crack at the famous Hubble palette as it was what got me interested in AP in the first place 5 years ago when I started out!  So the Elephant's Trunk nebula was my first but it was a bit low and I think the moonlight might not have helped my Sii and Oiii subs?  I am guessing from processing my subs that there is much less of this stuff about so I need proportionally longer/more subs to get it?  Secondly last night I wasn't even intending to capture anything I just snuck out seeing clear skies with a view to sorting a PHD2 gremlin, which I did, then realised the Californian nebula was in a good spot for me so shot away.  All captured with SG Pro and processed in Star Tools very roughly as I do not really know what i am doing there yet, but as this is my first time even combining mono subs I'm quite happy, I know they are rough but I see great promise with this camera once I sort out longer capture sessions and ideal gain settings etc.

Elephants Trunk had 70x30s of each Sii Ha Oiii unguided

Californian had a mere 15x60s of Ha & I tried longer subs of 10x120s for Sii & Oiii, they were guided just to test my PHD2 was sorted.

Darks & bias no flats.

Please give me you thoughts on what I've got and pointers for where the processing needs work?  PS. for the Elephants Trunk I focused once at the start then did just let it rip, and for the Californian I realised to my horror afterwards I forgot to even focus at the start!  I'm going to get a step focuser in a few days and let SG Pro take care of it. 

This has given me a massive confidence boost anyway and is a huge step change from colour DSLR work.  Thanks for looking!

 

 

[Notty]

In fact one question for you narrowband boys and girls, do you ever/is it ever worth adding a LUM layer?  i did actually try but it destroyed all the colour from the other layers, though this is probably my knowledge of Star Tools, it gives you the options to weight the R,G,B layers but not the LUM and I couldn't see a way round it so ditched it completely.

[geordie85]

I found this website to be very useful. 

http://bf-astro.com/hubblep.htm

 

[swag72]

This is looking to be a most promising start! I've never added a luminance channel (taken with a luminance filter)  to Narrowband data, but I do add Ha or a mixture of Ha/OIII/SII data as a luminance layer. It depends on the target and the data as to what I use for a luminance layer.

The Bob Franke method linked to by @geordie85 is an excellent starting point in PS to really get those more traditional Hubble palette colours

[Notty]

5 hours ago, swag72 said:

This is looking to be a most promising start! I've never added a luminance channel (taken with a luminance filter)  to Narrowband data, but I do add Ha or a mixture of Ha/OIII/SII data as a luminance layer. It depends on the target and the data as to what I use for a luminance layer.

I just tried using Ha on its own as a luminance layer, but it completely messed up the colouring in processing to an extent I couldn't recover it by changing the colour levels at all.  Part of me thinks this is right, as I'm then effectively doubling up on the Ha contribution to the whole thing so I need a combined layer of all three as you say above.  However, the Ha subs were so much stronger than the other two (SII almost invisible) that can anyone suggest what sort of stacking algorithm might make the most sense when trying to combine all three?  Obviously any kind of average will just end up with something dreadful as would median I'd have thought?

[Notty]

Another crack at the colours, but I seem to have limited scope in Star Tools to manipulate them in the way the Bob Franke tutorial describes, it's not really Hubble but I think the colours are an improvement? Gave up trying to combine it with a fake LUM from the three original channels, the extent of levels of the stacked combo was just too big... I couldn't make any sense of it anyhow!

 

[Filroden]

On 1/23/2017 at 13:19, Notty said:

I just tried using Ha on its own as a luminance layer, but it completely messed up the colouring in processing to an extent I couldn't recover it by changing the colour levels at all.

I've only got one limited set of data to work with having only recently bought a Ha filter so I'm a beginner at this. However, what I found was that you really need to saturate the colour for the Ha to carry it when it's used a luminance layer. The narrowband data is so much cleaner and easier to process to high contrast levels that the high luminance values wash out the colour.

I don't use StarTools but my basic process is to develop two images.

1) A mono Ha image which will become the luminance channel. I process this to maintain maximum detail.

2) A colour image (for me that's RGB with a blend of Ha in the red but for you it would be your chosen combination of HSO). As I will only be using the colour information I can blur this image and really pull out the colours (being careful to mask the stars so as not to create colour halos).

I then convert the RGB image into L*a*b colour space and extract the a and b channels, throwing away the L channel. I can then recombine the a and b channels with the Ha mono image as the new L channel.

I gave this a quick try with your jpg, so this isn't the best starting point but it shows there is more you can pull out of your colour data. You'll get much further with the original fits data.

You might also want to play around with different palettes. If your SII data is the weakest, you might want to map it to the colour you least want to see in the image. I'd try a HSO mapping with H to R, S to G and O to B, and see if that gives a stronger balance.

[cfpendock]

For a relatively short exposure time you've caught some nice detail.  Personally, I find this target much more rewarding in mono - i.e. just Ha, but for an initiation into narrowband, why not?  The link given by geordie85 above should giveyou the possibilities to develop the colours as you want them.

Chris

[Davey-T]

Hi Notty good to see you're progressing nicely and the kit is all behaving itself, always the first hurdle to surmount.

A few of us have been having a hack at the Cal' Neb' being as it's nicely placed and the general consensus is that 0111 is practically non existent and requires lots / long subs to drag it out, S2 on the other hand is quite strong.

Dave

[Notty]

5 hours ago, Filroden said:

I gave this a quick try with your jpg, so this isn't the best starting point but it shows there is more you can pull out of your colour data. You'll get much further with the original fits data.

You might also want to play around with different palettes. If your SII data is the weakest, you might want to map it to the colour you least want to see in the image. I'd try a HSO mapping with H to R, S to G and O to B, and see if that gives a stronger balance.

Hey thanks for having a play with that, that does look rather good - can I ask what you did to it?  I'm really off-piste with all this, trying different things and sometimes I get a result that looks great e.g. colours but then I find it impossible to replicate and have no idea what I did!  It's still great fun.  I tried the HSO approach but couldn't get anything pleasant looking out of that.  It's all good though, I love your comment about the Ha channel basically putting you in space.  For the short (a.f.a.i.c) integration times, I am blown away by the Ha subs from this little camera.

5 hours ago, Davey-T said:

A few of us have been having a hack at the Cal' Neb' being as it's nicely placed and the general consensus is that 0111 is practically non existent and requires lots / long subs to drag it out, S2 on the other hand is quite strong.

Indeed Davey,  this is my most pleasing looking process colour-wise.  I find Star Tools excellent in many ways particularly noise reduction but for colour manipulation I still have to resort to Photoshop aaarggh.

 

[Davey-T]

If you can get hold of a copy of January Astronomy Now there's an article on imaging the California Nebula by Nik Szymanek.

Dave

[Filroden]

1 hour ago, Notty said:

can I ask what you did to it? 

my basic process is to develop two images.

1) A mono Ha image which will become the luminance channel. I process this to maintain maximum detail.

2) A colour image (for me that's RGB with a blend of Ha in the red but for you it would be your chosen combination of HSO). As I will only be using the colour information I can blur this image and really pull out the colours (being careful to mask the stars so as not to create colour halos).

I then convert the RGB image into L*a*b colour space and extract the a and b channels, throwing away the L channel. I can then recombine the a and b channels with the Ha mono image as the new L channel.

I have no idea how to do that in StarTools but you can move between RGB and Lab in PI and in PS.

[Notty]

Thanks Ken I've just had some feedback from the man at Star Tools which leads me to think I should maybe master some "simple" RGB processing and capture first before jumping straight into tri-colour narrowband.  I kind of knew that anyway but couldn't resist, but in any case after his analysis of my stacks especially the LUM, SII and OIII, due to the extreme (and I mean vicious) gradient and vignetting which is overwhelming any signal which could be used for colour, it seems flats are not optional for my setup!  I did darks and bias for these but no flats, and I think this is going to be the key to progressing on this.  When I'm home I'll attempt some flats and see how terrible they look...